Subcutaneous Transmitter Development

© 2013-2019, Kevan Hashemi, Open Source Instruments Inc.

Contents

Introduction
Accelerated Aging
Circuit Versions
2013
2014
2015
2016
2017
2018
JAN-18FEB-18MAR-18APR-18
MAY-18JUN-18AUG-18SEP-18
OCT-18NOV-18DEC-18
2019
JAN-19FEB-19MAR-19APR-19
MAY-19JUN-19JUL-19AUG-19

Introduction

Here we record our work on the development, improvement, and quality assurance of our Subcutaneous Transmitters. We begin with a summary table showing the results of our accelerated aging reliability testes. We present the various circuit board versions we have made in our pursuit of ease and reliability of encapsulation. Our day-to-day record of work starts with the introduction of the A3028 transmitter in September 2013. For earlier records of development, see A3019 (2010-2014), and A3013 (2007-2011) manual pages. For early work on encapsulation see SCT Encapsulation. For radio frequency isolation see Faraday Enclosures. For flexible leads see Flexible Wires. For comparison of electrodes see Electrodes. For work on radio frequency reception see Data Transmission and Reception.

Accelerated Aging

[29-MAR-17] We started accelerated aging tests after discovering that a lot of one hundred A3028AV2 circuits was plagued by cracked capacitors as a result of excessive placement force during automated assembly. In the warmth and humidity of an animal's body, these cracks corroded and caused the capacitors to fail within a few days of implantation. Such corrosion takes place more quickly at higher temperatures, as presented in Hallberg and Peck. We began accelerated aging test in March, 2015. Since then, we have poached roughly one hundred transmitters in hot water until they failed by one means or another.

According to statistical mechanics, the rate at which a chemical reaction proceeds is proportional to eE/kT, where T is absolute temperature, E is the activation energy of the rate-determining step in the chemical reaction, and k = 8.6×10−5 eV is the Boltzmann constant. We expect the mean time to failure of our subcutaneous transmitters to be proportional to eE/kT. In Hallberg and Peck, the authors show that this relationship applies well to measurements of the mean time to failure for temperatures 20-150 °C and relative humidity 20%-100% when they use an activation energy of 0.9 eV. Their measurements came from studies of circuits assembled with tin-lead solder. For modern circuits, which are usually made with silver-tin solder, a better value for the activation energy may be 1.1 eV. The higher the value of E, the greater the acceleration of aging at a higher temperature. We assume an activation energy of 0.9 eV for corrosion in our circuits, so as to give us a conservative estimate of the acceleration caused by poaching at higher temperatures. Our devices operate at the rodent body temperature of 37°C = 310 K. When we perform an accelerated aging test at 60°C = 333 K, we expect an acceleration of at least ×10. At 80°C = 353 K we expect acceleration of at least ×60.

The following table summarizes our recent accelerated aging tests. For older tests see our archives. All tests in water in a sealed jar. Failures recorded on the day they are first detected. An "artifact" is a severe corruption of the EEG signal that appears after the start of the test. Examples of severe corruption are: gain versus frequency for 100-kΩ source is wrong by more than 3 dB, steps changes of ≥100 μV once every ten seconds, dynamic range compressed to less than 10 mV. A "failure" is a failure to transmit an EEG signal, however corrupted that signal might be by artifacts. Search the notes below with the transmitter serial number to get the details of each transmitter we poached.

Circuit
and Build
Battery Qty Start First
Artifact
(days)
First
Failure
(days)
Comments
GV1 B73028 BR1225 10 16JAN18 3 6 80°C, J3 CC6d, J13 UD6d, J5/J21 UD13d, J1/J7/J9/J11/J17/J19 FL14d. Nominal 15d.
GV1 B73028 BR1225 3 06MAR18 none 24 60°C, B200.78 FL24d, B200.81 FL24d, B200.82 FL24d. Nominal 26d.
GV1 B73028 BR1225 2 16MAR18 none 27 60°C, B205.9 FL27d, B205.13 FL28d. Nominal 26d.
RV3 B69610 BR2330 1 17APR18 NA 113 60°C, E206.130 TS113d. Nominal 130d.
GV1 B75204 BR2330 1 07MAY18 none 85 60°C, E200.119 TM85d. Nominal 130d.
PV1 B78457 CR1025 1 07MAY18 11 12 60°C, P1.90 FE12d. Nominal 36d.
PV1 B78457 CR1025 1 29MAY18 none 10 60°C, P1.89 UD10d. Nominal 36d.
GV1 B75204 BR1225 1 27JUL18 none 7 60°C, B200.91 TS7d. Noisy. Nominal 26d.
GV1 B75204 BR1225 4 27JUL18 none 24 60°C, B202.61 FL24d, B207.30 FL24d, B207.33 FL25d, and B207.34 FL25d. Nominal 26d.
PV1 B78457 CR1025 2 19SEP18 none 26 60°C, P207.41 UD26d, P207.45 FL33d. Nominal 36d.
GV1 B78082 BR1225 1 16OCT18 none 24 60°C, B206.193 FL24d. Nominal 26d.
GV1 B78082 BR1225 2 16OCT18 none 34 60°C, C206.157 FL34d, C210.7 FL41d. Nominal 40d.
GV1 B78082 BR2330 1 02NOV18 none 91 60°C, E210.25 CC91d. Noisy. Nominal 130d.
GV1 B78082 BR1225 2 20NOV18 30 31 60°C, C210.43 FL36d, C210.56 UD31d. Nominal 40d.
PV1 B78457 ML621 3 10DEC18 none 6 60°C, T19 FL6d, T20 FL6d, T21 FL6d. Nominal 6.5d.
GV1 B78082 BR2330 2 18DEC18 91 none 60°C, Inactive Test, D208.189, D208.193. 1 SS-5001, 1 MED-6607.
PV1 B78457 ML621 3 21DEC18 6 7 60°C, T19 FL7d, T20 FL7d, T21 FL7d. Nominal 6.5d.
PV1 B78457 CR1025 1 21DEC18 none 23 60°C, P207.73 UD23d. 3 MED-6607. Nominal 36d.
PV1 B78457 ML621 3 31DEC18 NA 15 60°C, Inactive Test, T19 CC64d, T20 UD15d, T21.
GV1 B78082 BR1225 1 10JAN19 none 33 60°C, K207.65 CS42d. Nominal 58d.
GV1 B78082 BR1225 1 10JAN19 none 33 60°C, K207.68 UD33d. Nominal 58d.
PV1 B79594 CR1025 1 15JAN19 NA 34 60°C, P207.105 UD34d. Nominal 36d.
PV1 B79594 CR1025 1 18JAN19 31 103 60°C, Inactive Test, P207.114 CC103d.
PV1 B79594 BR1225 1 05MAR19 none 12 60°C, S210.67 CC12d. Soldered batteries. Nominal 40d.
PV1 B79594 BR1225 1 05MAR19 12 41 60°C, S210.78 FL41d. Soldered batteries. Nominal 40d.
PV1 B79594 BR1225 1 05MAR19 none 9 60°C, S210.68 FL9d. Soldered battery. Nominal 8d.
GV1 B81441 BR1225 1 16APR19 none 20 60°C, B210.155 FL20d. Left on 1-5 days during encapsulation. Nominal 26d.
GV1 B81441 BR1225 1 16APR19 none 27 60°C, B210.167 FL27d. Noisy. Nominal 26d.
GV1 B81441 BR1225 1 28MAY19 none 24 60°C, B205.59 FL26d.
GV1 B81441 BR1225 1 28MAY19 none 27 60°C, B211.25 FL24d.
GV1 B85211 BR2330 1 22JUL19 none none 60°C, B200.125. Nominal 130d.
GV1 B85211 BR2330 1 22JUL19 none none 60°C, B200.126. Nominal 130d.
GV1 B85211 BR1225 1 13AUG19 none none 60°C, C207.137. Nominal 40d.
Table: Summary of Accelerated Failure Tests. The circuit problems are identified by two-letter codes. FL is "Full Life", CC is "Corroded Capacitor", CS is "Corrosion Short", UD is "Unidentified Drain", TM is "Transmit Malfunction", TS is "Temporary Shutdown", OG is "Out Gassing", FE is "Faulty Encapsulation". Time until we discovered the failure is after the failure code. If the poached transmitter had artifact problems at the beginning of the test, we enter "NA" for the first artifact time.

In the first tests, we did not take note of how we cooled the devices when we removed them from the oven to check them. In some tests we deliberately put them straight into cold tapwater to cool them rapidly. When three such transmitters failed within minutes of cooling, we suspected that thermal shock was a factor in the failures. For several months, we removed the devices from their poaching water and let them cool in air before testing. The resistive switch problem persisted, however, which suggests it is caused by condensation, not contraction. The resistive switch problem turned out to be due to dendrites growing between the pins of U1. We no longer take any particular precautions heating and cooling transmitters to and from 60°C, but we monitor their behavior during and after such changes, so as to catch failures that occur during expansion or condensation.

[15-NOV-16] Seven dual-channel A3028A mouse transmitters provided full performance in 80°C water for 11 days, during which corrosion equivalent to at least 660 days at 37°C took place. Four single-channel A3028E rat transmitters survived corrosion equivalent to at least 940 days at 37°C over the course of ten weeks at 60°C and 80°C. We conclude that that our transmitters will survive corrosion within an animal body for two years. This corrosion lifetime is separate from the operating life of the battery, which is set by the battery capacity and the transmitter's current consumption.

Circuit Versions

Aside from the assembly versions, we have versions of the circuit board that we use to build the A3028. The same circuit version can be used to make multiple assembly versions. The same assembly version can be constructed using multiple circuit versions. Here we list the more recent versions, the name of the printed circuit board they use, the type of capacitor, and what we know about the component assembly process.

Version PCB Large Capacitor Solder Wash Details
RV1 A302801D 10μF 10V X5R Samsung lead-free water X and Y 160 Hz, protected inputs, square pads, U3-1 rounded, lead-free BGA, solder paste stencil.
AV3 A302801E 10μF 10V X5R Samsung lead-free water X and Y 160 Hz, round pads, U3-1 square, lead-free BGA, fits BR1225, solder paste stencil
AV4 A302801E 2.2μF 10V X5R Taiyo-Yuden lead water X and Y 160 Hz, round pads, U3-1 square, lead-free BGA, fits BR1225, solder paste stencil
AV5 A302801E 10μF 6.3V X5R TDK lead chemical X 160 Hz, Y 80 Hz, round pads, U3-1 square, lead-free BGA, fits BR1225, solder paste printer
AV5LF A302801E 10μF 6.3V X5R TDK lead-free chemical X 160 Hz, Y 80 Hz, round pads, U3-1 square, lead-free BGA, fits BR1225, paste printer
RV2 A302801F 10μF 6.3V X5R TDK lead-free chemical X and Y 160 Hz, input protection, octagonal pads, U3-1 rounded, lead-free BGA, fits BR1225 or BR2330, solder paste printer, mounting wire pad
RV3 A302801F 10μF 6.3V X5R TDK lead-free chemical X 160 Hz, Y 80 Hz, input protection, octagonal pads, U3-1 rounded, lead-free BGA, fits BR1225 or BR2330, solder paste printer, mounting wire pad
RV4 A302801F 10μF 6.3V X5R TDK lead-free chemical X 80 Hz, Y 80 Hz, otherwise as RV3
RV5 A302801F 10μF 6.3V X5R TDK lead-free chemical X 160 Hz, Y 160 Hz, otherwise as RV3
RV6 A302801F 10μF 6.3V X5R TDK lead-free chemical X 320 Hz, Y 320 Hz, otherwise as RV3
RV7 A302801F 10μF 6.3V X5R TDK lead-free chemical X 640 Hz, Y 640 Hz, otherwise as RV3
GV1 A302801G 4×10μF 6.3V X5R TDK lead-free chemical X 160 Hz, Y 80 Hz, eliminate mosfet power switch, two anchor holes for mounting wire pad, dramatically reduced switching noise as a result of increased decoupling capacitors.
Table: Summary of Circuit Board Versions. Links are to bills of materials.

The GV1 comes ready-made from the assembly house for single-channel 160-Hz and single-channel 80-Hz transmitters, both 1.4-ml and 2.8-ml sizes. The GV1 eliminates the mosfet power switch present on earlier versions, which turned out to be redundant, and which was the source of the "resistive switch" failure in accelerated aging. The GV1 provides a total of 40 μF of decoupling on the battery voltage, which reduces switching noise down to below 1 μV rms in encapsulated transmitters. The GV1 offers input protection, which has no significant effect upon the recording of EEG, but which guarantees that the circuit will not be endangered by stimulation voltages applied to the brain near the EEG electrodes.

2013

See Development Archive.

2014

See Development Archive.

2015

See Development Archive.

2016

See Development Archive.

2017

See Development Archive.

2018

JAN-18

[02-JAN-18] Poaching transmitters G201.183 and G201.185 reception 100%. For channels 183, 185, 186 response to 100-kΩ sweep correct. For channel 183, response has correct shape but gain is 4 dB lower than 184. Report VB = 2.62 V and 2.60 V.

[08-JAN-18] Poaching transmitters G201.183 and G201.185 reception 100%. For channels 183, 185, 186 response to 100-kΩ sweep correct. For channel 183, response is 10 dB too low at 100 Hz. Report VB = 2.62 V and 2.53 V.

[09-JAN-18] We have batch B203_53 consisting of 8 of A3028B-H-AA, formerly known as the A3028N, head-fixture transmitter for mice. Frequency response B203_53 within &plumn;0.3 dB.

[11-JAN-18] Poaching transmitters G201.183 and G201.185 reception 100%. For channels 183, 185, 186 response to 100-kΩ sweep correct. For channel 183, response is 10 dB too low at 100 Hz for 50-Ω and 100-kΩ sweeps. Report VB = 2.60 V and 2.44 V respectively.

[12-JAN-18] Poaching transmitters G201.183 and G201.185 reception 100%. For channels 183, 185, 186 response to 100-kΩ sweep correct. Channel 183 response10 dB too low at 100 Hz. Report VB = 2.58 V and 2.43 V respectively.

We have 10 of A3028J-AAA made with the A3028GV1 assembly, unmodified to give the 160-Hz bandwidth on X and 80-Hz on Y.

[16-JAN-18] Poaching transmitter G201.183 still running, 100% reception, VB = 2.33 V. Response of channel 183 to 50-Ω sweep correct, for 184 it's 10 dB too low at 100 Hz. Transmitter G20-1.185 has stopped running. We start it again, VB = 2.1 V. Response to 50-Ω sweep of 5 mV is correct. It is 42 days since we started poaching, suppose 185 failed at 41 days, and suppose 183 would fail before tomorrow, or 43 days. Typical operating life for the A3028G is 42 days. These two devices we burned in for one day in the dry oven before poaching, so they delivered their full life. We end our test of both, diagnosis "Full Life". Silicone in perfect condition. Serial number label ink now dark gray rather than black. No corrosion around mounting wire stub. No separation of silicone from epoxy. Minimal corrosion of solder joints on electrode pins.

Our test batch of 10 of A3028J-AAA made with the A3028GV1 assembly have been soaking in water. No sign of rust. Switching noise less than 2 μV for all devices. Turn on and place in oven at 80°C to poach.

[19-JAN-18] Poaching transmitters all running with 100% reception. Response to 50-Ω sweep is correct for all except No13, which reports VA = 1.9V and cannot amplify its input.

[22-JAN-18] Poaching transmitters all running except No3 and No13, which have stopped and won't turn on.

[23-JAN-18] Eight poaching transmitters all running 100% reception and reponse to 100-kΩ sweep correct. Dissect A3028J No13. VB = 0.4 V. Disconnect VB = 0.4 V. Connect external 2.7 V. Inactive 1.4 μA, active 270 μA, nominal is 150 μA. Response to 100-kΩ sweep correct. VA = 2.58 V with VB = 2.73 V. Active 240 μA. Remove epoxy from C2 and C5. Active current 180 μA. Replace C5, active 150 μA. Heat up C4, active 140 μA. Replace C4, 140 μA. Replace C6, 160 μA. Remove C1, 170 μA. Remove C3, 160 μA. Remove R4 and R3, 130 μA. Remove U9, 60 μA. Replace U9 160 μA. Diagnosis "Corroded Capacitor", C5 in particular. We recall that No13 reported VA = 1.9 V, which is consistent with VB = 2.5 V and current 600 μA, which would drain the battery in three days, which is what happened. Dissect No3. VB = 0.4 V. Disconnect 0.5 V. Connect external 2.7 V. Inactive 1.9 μA. Active 139 μA. Reception 100%. Response to 100-kΩ sweep is a 1-Hz full-scale square wave on both channels. VC is stable. VA flucuates by 25 mV or so. The oscillation we associate with corrosion, but because we have no excess current at the moment, we won't be able to identify the source of the current drain. Diagnosis "Unidentified Drain".

We have batch A206_23 consisting of ten A2038A-DDC. We apply a 6.3-mV sweep A206_23. Switching noise in 37°C water ≤4 μV. Total noise in 2-160 Hz ≤15 μV rms after scrubbing the pins and screws twice, but up to 40 μV before due to rumble.

[24-JAN-18] Poaching transmitters No1, 5, 7, 9, 11, 17, 19, 21 still running. Report VA = 2.62-2.67 V except for No21, which reports 2.50 V. Gain for 100-kΩ sweep correct except for No7 X which is 6 dB too low at 100 Hz. We have B206.78 failed after encapsulation. Dissect. VB = 2.6 V. It turns on and off irregularly. Discard.

[25-JAN-18] Eight poaching transmitters still running with 100% reception.

[26-JAN-18] All eight poaching transmitters still running. Apply 100-kΩ sweep. No7 X gain 6 dB too low at 100 Hz, Y gain 6 dB too high at 60 Hz. No5 X channel gain 3 dB too low at 100 Hz. No21 gain of both channels 3 dB too high at 10 Hz. All other channels within 3 dB of nominal.

We have batch C206_88 consisting of 12 A3028C-CC. Apply 5-mV 20-MΩ sweep. Frequency response C206_88 within ±0.3 dB. Total noise <9 μV. Switching noise <8 μV in 37°C water.

[29-JAN-18] Poaching transmitter No19 VA = 1.9 V, No1 VA = 2.1 V response to 10-kΩ sweep attenuates above 60 Hz on both channels, No7 VA = 1.9 V seen on X with square wave on Y, No11 VA = 2.2 V but response of X is still correct for 0.3-160 Hz bandwidth, while response of Y is 6 dB too low at 80 Hz. No9 VA = 2.5 V, response of X 6dB too low at 120 Hz and of Y 6dB too low at 60 Hz, No17 VA = 1.9 V but still see some response on X and Y to sweep, No5 and No21 have stopped and won't turn on. They have run for 310 hours. Their expected life is 340 hours.

[30-JAN-18] Dissect poached No5. VB = 0.6 V. Disconnect, VB = 0.6 V. Connect external 2.7 V. Inactive 2.3 μA, active 138 μA. Response to 100-kΩ sweep is 6 dB too low at the high end of the pass band for both X and Y. Diagnosis "Unidentified Drain". Dissect No21. VB = 0.7 V. Disconnect, VB = 0.7 V. Connect external 2.7 V. Inactive 3.2 μA. Active 141 μA. Response to 100-kΩ sweep 6 dB too low at top end in X but perfect in Y. Diagnosis "Unidentified Drain".

Poaching transmitters No1 VA = 1.9 V, reception 60%. No7 turns off when it cools to room temperature. No9, No 11, No17, and No19 have all stopped. Dissect No1, VB = 2.0 V. Disconnect, VB = 2.6 V. Inactive 2.4 μA, active 140 μA. Response to 100-kΩ sweep 10 dB too low at high end of X and Y. Diagnosis "Full Life". Diossect No7, VB = 2.6 V, now turns on. Disconnect VB = 2.6 V. Connect external 2.7 V, inactive 2.4 μA, active 135 μA. 100-kΩ sweep response 6 dB too low at high end. Diagnosis "Full Life". We don't bother dissecting No19, No11, No9, and No17 because all have run for 340 hours, and typical life is 48 mA-hr / 140 μA = 340 hours.

We have batch B206_75 consisting of ten A3028B-AA. Gain within ±0.3 dB see B206_75. B206.87 has a sharp-edged breech in epoxy on battery rim with inadequate silicone cover. Reject. Total noise in 40°C water is <9 μV. Switching noise <5 μV.

FEB-18

[02-FEB-18] We have C206.102 a delayed member of an earlier batch. Gain versus frequeny matches the rest of the batch and switching noise in 37°C is 4 μV.

[09-FEB-18] We have batch B206_45 consisting of 9 of A3028A-DDC. Volume of five of them we measure in a beaker to be 6 ml, or 1.2 ml each. We measure the volume of a single transmitter by surface reflection with a precision of ±0.05 ml (one drop) and get 1.2 ml. Frequency respose A206_45 within ±0.3 dB. Switching noise in warm water is <4 μV.

[13-FEB-18] We have EEG/EMG recordings from Edinburge. The EEG electrodes are bare wires held in place with screws, one over cortex, one over cerabellum. The EMG electrode is bare wire in muscle with silicone cap screwed back on to secure. In twenty-five hours of recording there is not a single step artifact in the EEG. Here is the spectrum of an ewight-second interval.


Figure: EEG (Green, No1) and EMG (Blue, No2). Both channels 512 SPS. EEG amplifier 0.3-160 Hz. EMG amplifier 0.3-80 Hz.

Judging by the frequency response, we are guessing that this is an A3028J-AAA. We see switching noise of amplitude 5 μV rms.

[15-FEB-18] We receive M1513090524.ndf from Edinburgh University, a recording made of intercostal muscles using an A3028B. We see heartbeat and respiration.


Figure: Heartbeat and Respiration in 0-20 Hz Portion of Intercostal EMG. Taken from M1513090524.ndf 16-s interval starting at 48 s.

The heartbeat fundamental is at 6.3 Hz, with harmonics at 13 Hz and 19 Hz. Respiration fundamental is at 2.1 Hz with harmonic at 4.2 Hz.

[27-FEB-18] We have first article, 5 pieces, of A3028PV1. Here is the bottom side of the board:


Figure: Bottom Side of A3028PV1 Assembly.

We connect 2.7 V to the circuit and de-activate. Quisecent current fluctuating 0.5 to 1.0 μA. We look at VB and find the following 29-mV pulses with period 260 ms.


Figure: Pulses on VB Due to Magnetic Switch. Pulse period 260 ms.

We put a 1000-μF electrolytic capacitor across VB. After a while we measure a stable current of 0.8 μA. We disconnect the circuit and after a minute the capacitor itself draws 0.0 μA. Inactive current is 0.8 μA. We program with P3028P01 but oscillator U10 is not producing any signal, just 0V, and current is 400 μA. We set up a ring oscillator between TP1 and TP2 and see 131 MHz, current now 6.2 mA. It turns out we should set all inputs to HOLD, including those that we have used as layout bridges to power and ground pads within the BGA footprint. Having done this, active current is 24 μA. We have no RCK. We try a third assembly with the updated firmware and it works fine. With 512 SPS on X, current consumption is 70.4 μA. We re-program as A3028P, 128 SPS, 0.3-40 Hz, and see active current consumption 30 μA. We obtain the following frequency response with a 20-MΩ 5-mV sweep.


Figure: Frequency Response of A3028PV1 Amplifier.

We see a half-power frequency of about 45 Hz, with which we are well-satisfied. At 30 μA, expected operating life with a 30-mAhr CR1025 battery will be 1000 hrs. With 0.8 μA quiescent current, shelf life will be 52 months.

We have batch B200_55 consisting of 11 of A3028B-AA. Frequency response B200_55 within ±0.3 dB. Noise ≤12 μV in all, with some as low as 6 μV rms total noise from 1-160 Hz. Switching noise fundamental amplitude ≤4 μV in 37 °C water.

[28-FEB-18] We have batch B200_62 consisting of 12 A3028B-AA. Volume of nine bodies measured together by displacement in a beaker of water is 12 ml, making individual volume ≈1.3 ml. response B200_62 within ±0.3 dB. Noise <8 μV from 1-160 Hz. Switching noise fundamental amplitude ≤3.5 μV in 36 °C water.

MAR-18

[06-MAR-18] We place B200.78, 81, and 82 in the oven at 60°C to poach. We check their frequency response first with 20-MΩ sweep, and find it correct. We have B207.3 and 10 with epoxy before dipping in silicone and we find that they don't turn on. They consume 16 mA from an external supply. We observe 1V8 = 0.0 V and VD = 0.2 V. We believe there is a short under the logic chip from 0V to 1V8.

We remove U10, the oscillator, from an A3028PV1 assembly and program. When we turn on power to the logic and amplifiers, current consumption is 15 μA. We program two more complete A3028PV1, but in both cases U10 does not work, and current consumption is 50-100 μA. We attempt to replace U10 on three assemblies, each of which consume 15 μA without U10. We succeed temporarily in some cases, but cleaning and drying eventually reveal a bad joint under the BGA-4 package. We give up. We erase the logic chip on our single working assembly. We reprogram. We repeat. We try OFF for the pull-up setting and find that does not reduce current. We go back to HOLD. The board is still working fine, drawing 30 μA. We now suspect that U10 was broken during assembly.

[09-MAR-18] Poaching transmitters B200.78, 81, and 82 100% reception, response to 20-MΩ sweep correct. We have batch B207_1 consisting of twelve A3028B-AA. Two failed after epoxy encapsulation. We found they consumed 16 mA when active, and trace this drain to the logic chip, which is shorting the 1V8 power supply. Now we have nine left, after burn-in and three-day soak. Frequency response B207_1 within ±0.3 dB. Switching noise in 37°C water ≤3 μV, total noise ≤7 μV rms.

[12-MAR-18] Poaching transmitters B200.78, 81, and 82 100% reception, response to 20-MΩ sweep correct.

[14-MAR-18] Poaching transmitters B200.78, 81, and 82 100% reception, response to 20-MΩ sweep correct.

[15-MAR-18] Poaching transmitters B200.78, 81, and 82 100% reception, response to 20-MΩ sweep correct.

[16-MAR-18] Poaching transmitters B200.78, 81, and 82 100% reception, response to 20-MΩ sweep correct. We have 15 of A3028PV1 from assembly house. We program, calibrate, and test. Thirteen work perfectly. Active current consumption is 32 μA on average. Two have a fault with U10, the BGA-4 oscillator, circuits 0006 and 0015. There is no CK output and current consumption is 200 μA. We see nothing wrong with the way the chips are soldered. Below is bottom side-view of


Figure: X-Ray of U10 BGA-10 from Beneath And To The Side. Arrows show how the balls are flattened where solder joints are formed correctly.

We have batch B205_6 consisting of ten A3028B-DD and three A3028B-AA. Frequency response B205_6.gif within ±0.3 dB. In water at 37°C we see rumble on the DD transmitters, but <6 μV on the AA. After ten minutes, noise on the DD is still 50 μV or more. We scrub all the pins. Now we have noise <8 μV on all DD and noise <6 μV on the AA. Switching noise fundamental is ≤3 μA and second harmonic is ≤1.5 μV. Two have wrinkles in silicone following a failure of our heating system earlier this week. We reject these, leaving sufficient to complete the job. We put B205.9 and B205.13 in the oven to poach at 60°C.


Figure: A Bare Pup Transmitter Circuit. We have not yet attached the leads and antenna, but the 10-mm diameter battery is loaded.

We load batteries onto two non-functioning A3028PV1 circuit boards. We solder the positive terminal directly to the edge of the battery. We connect the negative terminal with a bent copper wire.

[19-MAR-18] All five poaching transmitters 100% reception and correct response to 20-MΩ sweep.

[20-MAR-18] All five poaching transmitters 100% reception and correct response to 20-MΩ sweep.

[21-MAR-18] All five poaching transmitters 100% reception and detect heartbeat.

[22-MAR-18] All five poaching transmitters 100% reception and correct response to 20-MΩ sweep. We have E206.110 failed after epoxy encapsulation. Dissect. VB = 0.5 V. Disconnect VB = 1.2 V. Connect external 2.6 V. Inactive 1.4 μA, active 190 mA. With 1.0V supply we still see 11mA, with 1.5V, 50 mA. Remove U4, 1.5V gives 50mA. Diagnosis: short from VD to 0V running through U1's channel resistance S3028E_1. We check a bare circuit that failed QA with 500 μA current consumption. It runs fine, except for this consumption from VD. We clean vigorously with hot pressurized water, no change.

We receive back from assembly house two A3028PV1 upon which U!0, the oscillator, produces no signal. Of one of the balls under U10-3 were broken off at the chip, we would expect the fault to be affected by pressing on the chip. We tried pressing on the chip but saw no change in current consumption nor a start-up of oscillation. Here is a side x-ray of one of the two U10s provided by our assembly house.


Figure: Bottom-Side X-Ray of Faulty U10 Showing All Balls In Place and Soldered to Circuit Board. The solder joints are on the top side of the balls in this view.

We remove the two oscillators by heating with a solder blob until they come off onto the blob. We place them top down on paper and look at them through a microscope. Ball U10-3 appears to have broken off in both cases, while the other balls are either still adhered to U10 or have come off when liquid. We soak in hot water to remove flux and obtain the following photograph.


Figure: Underside of Two Faulty U10 from A3028PV1. It appears that Ball U10-3 (VDD) has broken off at the package.

We note that U10, when deprived of VDD = 1.8 V is drawing up to 500 μA from U8 through U10-2 (see S3028P. After removing U10, both circuits consume only 15 μA. It is possible that both U10s have been damaged by U8 through U10-2. Subsequent mechanical connection of 1.8V to U10-3 through its broken solder ball does not start oscillation nor reduce current consumption. Broken solder balls like this were a persistent problem with our old BGA-5, as we described in 18DEC13

[27-MAR-18] All five poaching transmitters 100% reception. Response to 20-MΩ sweep is within 1 dB of correct for all but B200.81, which is 3 dB too low at 100 Hz. Response to 100-kΩ sweep is, however, within 1 dB for B200.81. Total noise ≤8 μV for B200.78, B200.81, and B200.82, which have bare wire electrodes, and ≤16 μV for B205.9 and B205.13, which have soldered pins. We remove the soldered pins and expose bare wire. Now the noise is ≤8 μV. The characteristics below give channel number, battery voltage, and noise in 2-160 Hz for a typical eight-second interval.

M1522157467.ndf 870.0 9 2.68 8.2 13 2.62 8.2 78 2.60 6.3 81 2.57 6.2 82 2.48 6.1

Battery voltage for the older three transmitters 78, 81, and 82 is 0.1 V lower than for the younger two. The older transmitters have been running for 500 hours. We expect them to run for another 120 hours.

We have batch E206_103 consisting of fifteen A3028E-AA made with A3028RV3 circuits. Response to 20-MΩ sweep E206_103 within ±0.3 dB. Total noise 2-160 Hz in 44°C water is ≤15 μV with switching noise fundamental ≤5 μV. We have batch B207_12 consisting of four A3028B-AA made with A3028GV1 circuits. Response to 20-MΩ sweep B207_12. In 39°C water, total noise 2-160 Hz is ≤10 μV, switching noise fundamental ≤4 μV.

[30-MAR-18] Poaching transmitters B200.78, B200.81, and B200.82 show some activity with low battery voltage when hot, but turn off when they cool down. It has been 580 hrs, which is within 10% of the expected 620 hours. Diagnosis: full life. Poaching transmitters B205.9 and B205.13 response to 20-MΩ sweep correct, 100% reception.

We have two physical prototypes T1 and T2 of the A3028P. Both are equipped with 0.5±0.1 mm leads and an antenna made of a 0.7±0.1 lead.


Figure: A3028P Prototypes.

Prototype T1 has one thick coat of epoxy with no touch-up and three coats of silicone. Its weight is 1.5 g. Its maximum thickness is 5.2 mm, minimum 4.5 mm. Estimated volume 0.9 ml. Prototype T2 has one thin coat of epoxy followed by touch-up and two coats of silicone. Its weight is 1.4 g. Its maximum thickness is 4.6 mm, minimum 3.6. Estimated volume 0.75 ml.

APR-18

[02-APR-18] Poaching transmitters B205.9 and B205.13 response to 20-MΩ sweep correct, 100% reception. Battery voltages around 2.6V. No rumble in signal. Both were off when we took them out of the oven. We may have turned them off on Friday.

[04-APR-18] Poaching transmitters B205.9 and B205.13 100% reception and detect heartbeat.

[05-APR-18] Poaching transmitters B205.9 and B205.13 100% reception, response to 20-MΩ sweep correct. Battery voltages at 25°C 2.38 V and 2.50 V respectivey.

[06-APR-18] Poaching transmitters B205.9 and B205.13 100% reception, response to 20-MΩ sweep correct. Battery voltages at 60°C 2.66 V and 2.62 V respectivey. We have batch B200_83 consisting of 22 of A3028B-AA with 45-mm leads. Volume of 9 together is 12 ml, average 1.3 ml. We change our amplifier gain comparison range from 1-130 Hz to 0.25-160 Hz. With this extended range, the amplifiers agree to ±1.3 dB, which is within a 3-dB spread, see B200_83. In water at 37°C total noise in 2-160 Hz is ≤11 μV. Switching noise fundamental ≤4 μV.


Figure: Noise of 22 A3028B-AA In Water at 37°C.

Of the 22, all pass quality control, but if we remove B200_85 and B200_91 we have maximum noise 9 μV and amplifier agreement ±0.9 dB, so we set them aside.

[09-APR-18] Poaching transmitters B205.9 and B205.13 100% reception, response to 20-MΩ sweep correct. Battery voltages at 30°C 2.38 V and 2.41 V respectivey.

[10-APR-18] Poaching transmitters B205.9 and B205.13 100% reception, response to 20-MΩ sweep correct. Battery voltages at 50°C 2.48 V and 2.53 V respectivey.

[11-APR-18] Poaching transmitters B205.9 and B205.13 100% reception, battery voltages at 55°C 2.45 V and 2.57 V respectivey.

[12-APR-18] Poaching transmitter B205.9 has stopped. B205.13 100% reception, battery voltage at 60°C 2.53 V. Response to 20-MΩ sweep correct.

[13-APR-18] Poaching transmitter B205.13 has stopped. We have batch E206_121 consisting of sixteen A3028E-AA. Gain versus frequency within ±0.7 dB in 0.2-160 Hz, see E201_121. We measure volume of bodies plus antennas and 30 mm of leads for 16 transmitters, avearge volume is 3.3±0.1 ml. We measure volume of 4 bodies to be 12 ml, or 3.0 ml each. These transmitters we allowed to drain of epoxy for less time than usual, resulting in more epoxy on the device, increasing their volume by approximately 0.2 ml. Noise in water at 45°C is ≤9 μV with switching noise fundamental ≤3 μV.

[17-APR-18] We put E206.130 in the oven to poach at 60°C. This device transmitted all zeros for a few minutes during quality control, so we rejected it.

We cut back the antenna of an A3028P transmitter from 50 mm to 5 mm, sealing the end after each cut with an acrylic coating. We immerse the transmitter in the same location in the center of a 250-ml beaker of water 25 cm from an A3015C loop antenna. We use our spectrometer to measure power received by the antenna.


Figure: Power Received from A3028P with Helical Antenna. Range 25 cm.

We place the A3028P with 5-mm sealed antenna up against the glass in a beaker of water in our faraday enclosure with one receiving antenna (position A). We obtain 100% at all locations on our ALT platform. Of 30 random locations in the enclosure, we obtain 100% reception in half, >90% in thirteen, and <20% in two. With two receive antennas we obtain 100% reception everywhere. We drop the transmitter in the bottom of the beaker, so it is horizontal (position B). We obtain 100% reception in 19 of 20 locations and 50% in 1 of 20.

We cut off the antenna entirely and seal with silicone. We cut back the 50-mm antenna on another A3028P to 20-mm. We place both transmitters in position A. We place on the ALT platform and move and rotate at random. We obtain 31% reception from the 20-mm antenna and 69% from the 0-mm. We compare an A3028E with 50-mm loop antenna in position B, an A3028P with 0-mm in A and an A3028P with 15-mm in A, recording simultaneously with one antenna. We get 100.0%, 93.7% and 76.5% reception respectively. We cut back the 15-mm antenna to 10 mm and repeat. We get 96% from the A3028E, 88% from the 10-mm and 55% from the 0-mm. We cut back the 10-mm to 5 mm. We get 99.1% from the A3028E, 98.1% from the 5-mm and 61% from the 0-mm.

[20-APR-18] We repeat the above experiment with the same transmitters in the same positions, but the beaker is empty. We get 99.9% from the A3028E, 54.7% from the 5-mm and 0.9% from the 0-mm. We pour water in and repeat. We get 99.9% from A3028E, 98.3% from 5-mm and 61.7% from 0-mm. We load a new 13-mm antenna in place of 0-mm. We try A3028E in water B, A3028P 5-mm in water A and 13-mm outside the wall of the beaker, in air, position C. We have double-coated the 5-mm antenna in acrylic to make sure it's isolated. We get 98.8% from A3028E B, 92.3% from 5-mm A, 92.8% from 13-mm C. We double-coat the 13-mm in silicone and place it in water along with the 5-mm in position A. We get 99.5% from A3028E, 91.7% from 5-mm and 99.0% from the 13-mm. We empty the beaker, leaving A3028E in B and the 5-mm and 13-mm antennas in C. We get 99.9% from A3028E, 61.4% from 5-mm, and 95.1% from 13-mm.

The 13-mm antenna gives us over 90% reception in air, in water, or near water. We connect two antennas inside our enclosure and measure reception from A3028E in water B and 5-mm and 13-mm antennas in water at A. We get 99.9% from A3028E, 99.3% from 5-mm, and 98.0% from 13-mm.

[23-APR-18] Poaching transmitter E206.130 100% reception, VB = 2.77 V, response to 20-MΩ sweep correct.

[26-APR-18] Poaching transmitter E206.130 100% reception, transmits all zeros as it did during quality control.

[27-APR-18] We have batch E200_107 consisting of sixteen A3028E-FB, one coat SS-5001 and one outer coat of MED-6607. Frequency response E100_207 within ±0.8 dB. Switching noise in 35°C water ≤3 μV, total noise ≤11 μV.

[30-APR-18] Poaching transmitter E206.130 still running 100%, transmits all zeros.

MAY-18

[01-MAY-18] We have batch B206_139 consisting of 12 A3028B-AA. Volume of 8 together is 10.0 ml, or 1.25 ml. Frequency response B206_139 within ±0.5 dB. Total noise in 37°C water is ≤8 μV, switching noise fundamental ≤4 μV.

[07-MAY-18] Poaching E206.130 100% reception, transmits all zeros. Add to poach P90, prototype pup transmitter, and E200.119.

[10-MAY-18] Poaching E206.130 100% reception, transmits all zeros. P90 and E200.119 response to 20-MΩ sweep correct, 100% reception.

[14-MAY-18] Poaching E206.130 100% reception, transmits all zeros. P90 and E200.119 response to 20-MΩ sweep correct, 100% reception. Noise <8 μV, switching fundamental <1 μV in 60°C water.

[15-MAY-18] Poaching E206.130 100% reception, transmits all zeros. P90 and E200.119 response to 20-MΩ sweep correct, 100% reception. P90 VB = 3.01 V, E200.119 VB = 2.83 V.

[16-MAY-18] Poaching E206.130 100% reception, transmits all zeros. P90 and E200.119 response to 20-MΩ sweep correct, 100% reception. P90 VB = 3.01 V, E200.119 VB = 2,83 V. We see red and white corrosion inside the silicone at the base of the leads and antenna, especially where we burned away the epoxy to re-solder the antenna before re-applying silicone.

[18-MAY-18] Poaching E206.130 transmitting X again. All three E206.130, E200.119, and P90 response to 20-MΩ sweep correct and 100% reception. P90 VB = 2.95 V, E200.119 VB = 2.82 V, E206.130 VB = 2.84 V.

[21-MAY-18] Poaching E206.130, E200.119, and P90 response to 20-MΩ sweep correct and 100% reception.

[22-MAY-18] Poaching E206.130, E200.119, and P90 response to 20-MΩ sweep correct and 100% reception.

We have batch P1_89 consisting of 11 of A3028P-AA. Frequency response P1_89 within ±0.5 dBm. Noise ≤4 μV in 2-100 Hz. Transmit center frequencies in range 913-918 MHzz. We have three breaches in the silicone, which is too thin. We dry out and add another coat of silicone, making three coats total.

[24-MAY-18] Poaching E206.130, E200.119 response to 20-MΩ sweep correct and 100% reception. P90 100% reception and amplifiers and filters still working, but the baseline signal is swinging around, with bumps a few times a second.

[25-MAY-18] Poaching E206.130, E200.119 response to 20-MΩ sweep correct and 100% reception. P90 100% stops transmitting. We find that its antenna has corroded through at the base under our failed silicone patching. Even the antenna pad has corroded all the way through the circuit board, and the X− lead beside the antenna. Battery voltage 2.2 V. External 2.7 V, inactive 0.8 μA, active 19 μA. Diagnosis, Faulty Encapsulation.

[29-MAY-18] Batch P1_89 consisting of 12 of A3028P-AA now has three coats of silicone. No sign of rust or corrosion after five-day soak. Total noise in 0.5-40 Hz is ≤3.5 μV. No trace of switching noise. Reception 100%. Volume of 10 pieces is 6.0 ml. Mass is 1.41±0.01 g.

We add P1.89 to poach. It has three coats of MED-6607 and a 5-mm helical antenna. Poaching transmitters P1.89, E200.119, E206.130 battery voltages 2.92 V, 2.83 V, 2.81 V and reception 100% in water. Response to 20-MΩ sweep correct.

JUN-18

[01-JUN-18] We receive 30 of A3028PV1, build B76438. We test 26, 9 work. Of the 17 that fail, 2 have U10 working but consume excessive current (9 mA in No17, 0.11 mA in 07) until we remove U10, ASTMTXK, then current drops to 15 μA. Another 2 have the oscillator frequency varying with time, 4-6 kHz gradually, then fluctuating rapidly (22 and 11). The remaining 13 have U10 generating no signal and consume 30-300 μA. We remove U10 from half of these and current in every case drops to 15 μA. We re-program and feed 32.768 kHz in through TP1 and all these boards work perfectly. Of the 9 that work, 2 end up consuming 85 μA and 95 μA so we remove U10 and reprogram to show that U10 was responsible for the excessive current.

[04-JUN-18] With new magnifiers, we load new U10 onto five A3028PV1 circuit boards, dry, and calibrate. Current consumption 73.5-77.7 μA. Poaching transmitters P1.89, E200.119, E206.130 reception 100%, response to 20-MΩ sweep correct.

[05-JUN-18] We replace U10 on another 11 of our A3028PV1 circuit boards and all are now working. We cannot replace U10 on 3 boards because the solder mask over the track leading from U10-3 has come off and the exposed coper wicks the U10-3 solder ball all the way to U4-3. We revive two boards from the previous build and they work. We are left with 4 un-touched boards, 2 with fluctuating oscillators, and 23 working. We take a working board and erase the logic chip, but U10 still works. If we drive U10's output with the logic pin, current consumption increases bny 200 μA but U10 works after re-programming. We hear from assembly house, "We suggest running using a LeadFree profile and Leaded solder if they want to continue using this part. Additionally we will place notes for handling glass parts on this board. If this is sufficient then we will need to notify ENG to update paperwork."

We have batch D208_157 consisting of 12 of A3028D-DDA. Frequency response D208_157 within 0.5 dB, noise 2-160 Hz <10 μV, switching noise <3 μV.

[08-JUN-18] Poaching transmitters E200.119 and E206.130 still running, but P1.89 has stopped.

[11-JUN-18] Poaching transmitters E200.119 and E206.130 100% reception and response to 20-MΩ sweep correct. Dissect P1.89. Silicone well-adhered. No signe of corrosion. VB = 0.1 V. Disconnect, VB = 0.1 V. Connect external 2.7 V. Inactive 0.8 μA, active 34 μA. Reception 100%. Response to 20-MΩ sweep correct. Diagnosis "Unidentified Drain".

[15-JUN-18] Poaching transmitters E200.119 and E206.130 100% reception and response to 20-MΩ sweep correct for E200.119, but 6 dB too low at all frequencies for E206.140. VA = 2.81 and 2.74 V respectively.

[19-JUN-18] We place 5 of A3028P3 bare circuits with fresh batteries soldered to the boards, and 20-mm antennas, in our big faraday enclosure. The A3028P3 runs at 512 SPS and its current consumption is around 75 μA. We expect 400 hrs of operating life. Poaching transmitters E200.119 and E206.130 100% reception, VA = 2.84 and 2.78 V respectively at 60°C. E200.119 response to 20-MΩ sweep correct. E206.130 response to 20-MΩ sweep 20 dB too low, response to 50-Ω sweep correct.

We unpack 3 of our A3028PV1 assemblies. We connect 2.6 V and scrape the solder mask from the track leading between U10 and U8. In 2 circuits we see a 1.8-V, 32.7 kHz square wave. In 1 circuit we see 0 V. We program all three boars. We see 85 μA and 95 μA operating current in the first two boards, with the 32.7 kHz appearing on TP2. We see 29 μA on the third board, with no 32.7 kHz. The nominal operating current is 75 μA. With the oscillator removed we expect 15 μA. These three examples of U10 are consuming 10 μA, 20 μA, and 14 μA.

We receive recording of baseline and picrotoxin seizures from an adult mouse with an A3028P-AA implanted at ION/UCL. Baseline amplitude is 40 μV rms. Seizure spikes 1 mV, see here. Average reception in two hours of recordings is 98% with 97% of intervals having ≥80% reception.

[22-JUN-18] We have batch B202.43 consisting of 9 A3028B-DA. We add B200.85 to make ten. Frequency response B200_43 is within ±0.4 dB. Total noise 2-160 Hz in 37°C water after scrubbing pins is ≤10 μV, switching noise ≤5 μV. But B202.49 shows intermittent steps of several millivolts, even after scrubbing the leads twice and isolating it in its own beaker. We find a strand of antenna wire sticking through the silicone.

[25-JUN-18] We have B204.49 after removing stray wire and coating twice with silicone over the cut end. We place in water at 37°C. We scrub the lead tips. No sign of the intermittent steps we saw earlier. Noise is 10 μV rms 2-160 Hz. Removce from water and place in air. See no rumble. Noise is 9 μV.

We send four ASTMTXK oscillators back to the manufacturer, here they are arranged on a gel back with symptoms listed, as observed when they arrived from assembly house, and a few weeks later.


Figure: Four ASTMTXK for Return. We removed parts with iron at 500°F, washed, wiped dry on microfiber cloth, then placed in gel pack.

The balls are no longer intact on the bottom of each BGA-4, but we make sure each pad has a coating of solder.

[03-JUL-18] We have batch P204.140 consisting of three A3028P3-AA. Frequency response P204_140 correct, noise ≤6 μV in 2-160 Hz, switching noise <0.4 μV.

[04-JUL-18] We have batch B207_18 consisting of fifteen A3028B-AA. When we have added a drop of silicone to cover the tips of the antenna wires, and in a few cases this drop has a cavity, but the problem is cosmetic only. Frequency response B207_18 with ±0.5 dB. Switching noise in 37°C water ≤3.2 μV, total noise 2-160 Hz ≤8 μV.

Poaching transmitters E200.119, E206.130 reception 100%. E206.130 VA = 2.7 V. E200.119 response to 20-MΩ sweep correct, VA = 2.85 V.

[19-JUL-18] Poaching transmitters E200.119, E206.130 reception 100%. E206.130 VA = 2.62 V. E200.119 response to 20-MΩ sweep correct, VA = 2.78 V. Our discharge of five CR1025 batteries by five A3028P3 circuits is complete.


Figure: We discharge five CR1025, 30-mAhr, 3-V cells with five A3028P3 transmitters, channel numbers given in legend, each consuming ≈75 μA.

Average battery life it 400 hrs, expected is 400 hrs, range is ±2.5%.

[24-JUL-18] Poaching transmitters 100% reception. We have batch B202.56 consisting of 11 of A3028B-DA. Frequency resposne B202_55 within ±0.7 dB, switching noise in 37°C water ≤3.5 μV, total noise ≤12 μV (there are pins soldered to the lead tips). We can see the red top side of the circuit board at the corners, the epoxy is so thin. But silicone coating is firm.

[27-JUL-18] Poaching transmitters E200.119, E206.130 reception 100%. E206.130 baseline fluctuating. E200.119 response to 20-MΩ sweep correct, VA = 2.75 V. We add four of A3028B to poack: B200.91, B202.61, B207.30, B207.33, and B207.34.

[31-JUL-18] Poaching transmitters B200.91, B202.61, B207.30, B207.33, and B207.34 reception 100%, response to 20-MΩ sweep correct, VA = 2.68±0.1 V, noise <7 μV, except for No91, which is 11 μV. Poaching transmitter E206.130 reception 100%, fluctuating baseline. E200.119 stopped. Dissect. VB = 2.63 V. Disconnect battery, VB = 2.92 V. Connect external 2.6 V, active current 960 μA, inactive 1.7 μA. We find that VB = 2.63 V but VA = 2.27 V, suggesting 360 μA through R4. Heat up C4 and now current is 310 μA, 1V8 = 1.8 V. Sleep-wake and current is 969 μA again, but 1V8 = 1.8 V still. VC = 1.8 V. Clear epoxy from around C3 and U9-8 with intent to measure VD. But now the transmitter draws 80 μA and we receive from channel 130. Soon after, it's back to 960 μA and VD = 2.6 V. Now VA = VB = 2.6 V, !SHDN = 0V, TUNE = 0.44 V and VA = 2.3 V. The logic chip is getting stuck in one of its transmit states. Pull off battery. Active 81 μA, reception 100%. Connect external battery. Response to 20 MΩ sweep 10 dB too low but otherwise correct. Check CK and find its period is 32.8 kHz and 0-1.8 V logic levels. There is a cavity in the epoxy between U9-3, C13, and R13. Diagnosis "Transmit Malfunction".

AUG-18

[03-AUG-18] Poaching transmitters B202.61, B207.30, B207.33, and B207.34 reception 100%, response to 20-MΩ sweep correct. B200.91 has stopped. Cannot turn it on. E206.130 reception 100%, fluctuating baseline.

[06-AUG-18] Poaching transmitters B202.61, B207.30, B207.33, and B207.34 reception 100%, response to 20-MΩ sweep correct. E206.130 has switched itself off, can turn it on again. Dissect B200.91. Silicone well-adhered. No cuts or cavities. No sign of corrosion. VB = 0.2 V. Disconnect VB = 0.2 V. Connecct external 2.7 V. Inactive 2.8 μA. Active 83 μA. Recaption 100%, response to 20-MΩ sweep correct. Later, inactive current is 2.0 μA and active current is 78 μA.

[07-AUG-18] Poaching transmitters B202.61, B207.30, B207.33, and B207.34 reception 100%, response to 20-MΩ sweep correct. B200.91 active 78 μA, inactive 2.0 μA. Dissect E206.130. Silicone well adhered. No sign of corrosion. VB = 2.8V. Connet external 2.7 V. Active 85 μA, inactive 1.7 μA. Diagnosis "Temporary Shutdown". Repair three of four A3028PV1 circuits by loading SiT1552 for U10. We load a total of four chips and all four work. One we replace because the U10-1 ball was missing, but it worked anyway. The fourth board we could not fix because solder mask is missing from U10-3 to U4 and the track wicks away the ball.

[16-AUG-18] Poaching transmitters B202.61, B207.30, B207.33, and B207.34 reception 100%, response to 20-MΩ sweep correct. A3028P1 transmitter No97 equipped with 0.5-mm wires has been implanted in an adult mouse at ION since 18-JUN-18, but left off. On 30-JUN, 08-AUG, and 09-AUG we turn on the transmitter for a few hours and it records EEG. We receive this report from manufacturer of ASTMTXK oscillator, which we use for U10 in the A3028P devices, showing physical damage to the part around the solder balls, which suggests that the devices were damaged by the pick and place machine. We will have these parts hand-placed in our next assembly job. We receive fine recordings of cortical spreading depressions (CSDs) following seizzures in adult mice using our DC-160 Hz A3028U transmitters.

[17-AUG-18] We have batch C206_157 consisting of 11 of A3028C-CC. Frequency response C206_157 within ±0.7 dB, switching noise fundamental ≤3 μV, total noise ≤8 μV.

[20-AUG-18] Poaching transmitters B202.61 and B207.30 have stopped. B207.33 and B207.34 100% reception, response to 20-MΩ sweep correct for No33, 6 dB too low for No34. Battery voltages 2.52 V.

[21-AUG-18] B207.33 and B207.34 have stopped. We have three A3028T1-R, 0.3-40 Hz with A3028PV1 circuit and ML621 Li-Mn battery 6.8 mm in diameter. We measure battery voltage and get 2.66 V, 2.66 V, and 2.60 V. Looking at our discharge plots, it looks like the batteries are over 90% full. We connect the first one to 3.2 V through 400 Ω and see 400 μA flowing in with 2.92 V across the battery. After a few minutes, disconnect and see battery voltage 2.72 V.

[31-AUG-18] We have batch T209_1 consisting of three A3028T1-R. Frequency response T209_1 correct. Switching noise in 37°C water ≤3 μV, total noise ≤6 μV, see spectrum. Battery voltages 2.55 V, 2.49 V, and 2.46 V. Looking at discharge curves for the ML621 we conclude we must top up the charge of all three devices. We connect T209.1 and T209.2 through 1 kΩ and a microammeter to 4.2 V. Both are turned off. Each draws 130 μA separately, and together they draw 240 μA. If we turn either transitter on, it draws up to 500 μA with full-scaled steps on X. We leave to charge with 4.0 V connected directly to the 1-kΩ charging resistor.

SEP-18

[04-SEP-18] Devices T209.1 and T209.2 have been charging for four days. Current from 4.0 V through 1.0 kΩ is now 6.2 μA. Assuming 3 μA into each device, the charging diodes will each drop 0.45 V, so the voltage on the battery should be around 3.1 V. We place them both in water with T209.3. Battery voltages are 3.24 V, 3.17 V, and 2.41 V respectively. Noise at 25°C is 4.3 and 4.2 μV with switching noise <1 μV. Connect T209.3 to 4.0 V through 1 kΩ and see 90 μA flowing in. Leave to charge up.

[06-SEP-18] Our A3028T1, T209.3 is charged to 3.15 V. We have recorded its charge current with time from a 4.0-V supply through a 1-kΩ resistor.


Figure: Charging Current versus Time for ML621.

We leave T209.1 running in our faraday enclosurefrom 9:30 am 06-SEP-18.

[10-SEP-18] Our A3028T1 T209.3 battery voltage is 2.2 V. Response to 20-MΩ sweep correct.

[11-SEP-18] Our A3028T1 T209.3 battery voltage is 2.14 V. Response to 20-MΩ sweep correct, but we must perform the sweep with a 5-mVpp sweep rather than 10-mV sweep because the dynamic range is now −17…+4 mV. Transmitter has been running for 127 hours.

[12-SEP-18] Our A3028T1 T209.3 battery voltage is 2.05 V. Response to 20-MΩ sweep correct. Transmitter has been running for 144 hours.

[14-SEP-18] Our A3028T1 T209.3 has stopped. Our recording shows battery voltage 2.00 V after 150 hours. We charge the battery from 4.0 V through 1 kΩ. We have batch P207_35 consisting of 17 A3028P1-AA. Volume of all seventeen including leads and antenna is 11 ml, making individual volume 0.65 ml. Response to 20-MΩ sweep P207_35 within ±0.6 dB. Total noise ≤5 μV rms, switching onise ≤0.6 μV. One of the fifteen, P207.49, won't stay on.

[19-SEP-18] We place P207.41 and P207.45 in the oven to poach at 60°C. Battery voltages are both 2.96 V. Both are P3028P1-AA, but P207.41 required re-work after epoxy encapsulation, burning away epoxy to re-attach the X+ lead.

[24-SEP-18] Poaching transmitters 100% reception. P207.41 has wandering baseline and does not respone to frequency sweep. P207.45 correct response.

[26-SEP-18] Batch B206_190 consists of four devices, two new and two previously checked. Frequency response B206_190 correct, noise ≤8 μV, switching noise ≤4 μV at 35°C. Poaching transmitters 100% reception. P207.41 has wandering baseline and does not respone to frequency sweep. P207.45 correct response.

[28-SEP-18] We have three A3028T1-R encapsulated with epoxy that fail quality assurance. T209.7 lost its X lead. The other two fail to transmit. The two that fail to transmit both have the same problem: the battery cannot supply 32 μA of operating current. Its voltage drops to 1 V. When supplying the inactive current of 0.8 μA, its voltage is 2.2 V. We connect 3.2 V through 1 kΩ directly to battery T209.6 and see only 7 μA flowing in. Battery T209.11 accepts a 90-μA recharge current. Its battery voltage is 3.1 V. As soon as we disconnect the charging voltage, the battery voltage drops to 2.2 V. We connect 4.0 V through 1 kΩ to the X leads of T209.7 and see 1 mA flowing in.

We take the same ML621 with solder tabs we used for our ML-series recharge experiments. Its votltage is 3.00 V. Apply 500°F iron for ten seconds, clean off flux with water, now 2.92 V. Repeat, voltage 2.86 V. Repeat, and after 9 s the battery voltage drops suddenly to zero. Take out a fresh ML621 from its package. Measure 2.78 V. Apply 500 F and after 10 s the battery voltage drops to 0 V. Apply 500°F for 3 s on, 3 s off, on fourth heating, battery voltage drops to zero. We take a fresh ML621. We load it with 1 kΩ for ten seconds. Its voltage is 2.67 V. We load with 1 kΩ. Voltage drops immediately to 2.49 V, implying output resistance 72 &Omegal;. After one minute, 2.32 V. Disconnect, after five minutes battery has recovered to 2.69 V. Apply 500°F for three seconds, 2.72 V. Apply 1 kΩ, drops to 2.58 V, implying 56 Ω. Apply 500°F for 3 s again, 60 Ω. Apply 500°F for 14 s and voltage goes to 0.00 V. We notice a sweet smell. The plastic ring that separates the terminals has bulged up and out of its slot. The failure is a sudden short-circuit.


Figure: An ML621 With Tabs Soldered to a Blank A302801P Circuit Board. The solder blob on the battery is formed on the cut end of the negative terminal, rather than directly on the battery case. Twenty seconds of heating this solder blob to 500°F fails to heat the battery up to more than 60°C.

Another fresh battery, soldered by tabs to a circuit board, as shown above, has voltage 2.61 V before 1 kΩ load, 2.45 V immedaitely after, for 64 Ω. Short circuit for ten seconds, voltage recovers to 2.45 V after one minute. Apply 500°F to the cut-off battery tab on the 0-V terminal for 20 s, battery voltage stable at 2.58 V.


Figure: BAS116LPH4 Forward Voltage with Current at Various Temperatures. There are two such diodes in the A3028P circuit. We have to extrapolate the 25°C line below 10 μA to estimate the drop at 3 μA.

When we charge the ML621 through the X leads of an A3028T-R, we do so through the 65-Ω resistance of each of its two 27-mm leads, and two BAS116LPH4 diodes. At the end of a re-charge, the current is of order 4 μA. At 25°C, the diodes will each drop 0.5 V. The temperature in our laboratory is, however, closer to 20°C. According to our calculations, the diode voltage should be around 0.52 V, so both of them together are 1.04 V. When we apply 4.0 V, the voltage on the battery will be 4.0 V − 1.04 V − (1120 Ω × 3 μA) = 2.96 V. We have had success charging with 2.9-3.3 V in the past.

OCT-18

[02-OCT-18] Dissect T209.7. Active current consumption with external 2.6 V is 35 μA. Connect batterty. When inactive, voltage is 2.4 V, when active, 2.3 V. We charge battery directly with 3.2 V and 1 kΩ and see 20 μA. We charge with 4.0V and 1 kΩ on the X leads and see 1 μA. There appears to be 1.2 V across D1 with only 1 μA. Something is wrong with internal connections. We connect 20-MΩ 20-Hz 30-mV and see gain varying by a factor of two over the course of seconds. Dissect T209.18. Active 32 μA with external 2.6 V. Battery shows 2.4 V when inactive, dropping to 1.2 V when active. Charge with 3.3 V and 1 kΩ see 20 μA flowing in. Battery is damaged. Dissect T209.13. Active and inactive current 15 mA, no transmission. Battery drained to 1.1 V. Connect 3.3 V through 1 kΩ see 500 μA. After five minutes, disconnect charger and battery is at 2.6 V. Connect to circuit of T209.7 and we see transmission. Battery was drained by excessive current consumption of T209.13, but recovered.


Figure: A3028T-R Discharging. No3 failed QA and we charged it twice for >48 hr through its X leads with 4.0 V and 1.0 kΩ. Later we charged it with 4.2 V. The others are discharging immediately after epoxy encapsulation (AE).

The T209.7 device runs well, but only for 110 hrs after its first re-charge, and only for 75 hrs after its second re-charge. We connect it to 4.2 V to see if we can get it to a full 5 mA-hr. The remaining six discharge curves shown above are consistent with 160-hr operating life, if we accept that No8 and No9 batteries were discharged during assembly and encapsulation.

[03-OCT-18] Poaching transmitters 100% reception. P207.41 has wandering baseline and does not respone to frequency sweep. P207.45 correct response to 1-200 Hz 20 MΩ sweep.

[05-OCT-18] We have batch P206_171 consisting of 15 A3028P2-AA. Frequency response P206_171 within ±0.8 dB. Noise <5 μV, switching noise <0.5 μV. We identiy our copper spade-end alligator clips as the source of our problems while attempting to charge a set of eight A3028T1-R. We solder gold pins to the leads of one of the devices, but the contact is intermittene between the copper clips and gold or steel. We heated the copper clips with a 650°F soldering iron to assemble them into an eight-position charging fixture, but we see no visible sign of oxide on the surface. And yet the contact resistance varies with pressure and moisture. When measuring the frequency response of batch P206)_171 with these clips, we several times see gain 20 dB too low at 1 Hz rising to correct at 100 Hz, suggesting a contact that resists DC current. We replace all clips with tin-coated steel clips, the same we have been using for years, and all these intermittent problems cease, but we are left with the difficulty of grasping the 2-mil diameter stainless steel wire with such a clip.

[08-OCT-18] Poaching transmitters 100% reception. P207.45 VA = 3.0 V at 60°C, correct response to 1-200 Hz 20 MΩ sweep. P207.41 wandering baseline. Of the eight A3028T1-R we left charging over the weekend, 6 have charge current around 10 μA and two appear to have become disconnected. The 6 have VA 2.9-3.2 V when we turn them on. The 2 have VA = 2.5 V. We re-connect the 2 and see 40 μA flowing into each. We leave them charging. The 6 we leave to run in enclosure.

[09-OCT-18] We have batch Q206_190 consisting of 7 of A3028Q-DNA. We measure the thickness of the epoxy encapsulation and obtain an average value of 9.61 mm, and after one coat of SS-5001 and one coat of MED-6607 we get 11.24. So the silicone coat has thickness 0.82 mm. Frequency response Q206_193 within ±0.7 dB over 0.25-350 Hz, noise 2.0-320 Hz ≤10 μV, switching noise <0.5 μV. We see no switching noise peak in any channel. Poaching transmitters 100% reception.

[10-OCT-18] Poaching transmitters 100% reception. We examine the discharge curves for eight A3028T1-R we finished recharging two days ago, see here. Included in the plot are three discharges of the No3 device. The 72-hr discharge followed a recharge with 4V and copper clips, 112-hr followed 4V and steel clips, 116-hr followed 4.2V and steel clips. We are using only steel clips now. No4, 5, 10, 12, 14, 17 charged up to 2.9-3.3 V with 4.2V and subsequently their discharge remains above 2.5 V for 20 hours. No8, 9 charge to only 2.6V, even though their final charging current is 50 μA each. Their voltage does not rise farther. During discharge, they drop below 2.4V in ten hours. We reject No 8 and No9. We suspect they were damaged during assembly. We leave them to discharge further, and remove the other six, turn them off, and connect them to our group charger. Total charging current is 800 μA.

[12-OCT-18] Poaching transmitters 100% reception. P207.45 correct response to 1-1000 Hz 20 MΩ sweep. P207.41 wandering baseline. We have six of A3028T1-R-AA on our recharger, 4.2V supply with individual 1 kΩ resistors. Total charge current after 45 hours is 28 μA. We disconnect each in turn and so obtain final charge currents No10 7 μA, No5 0 μA, No12 1 μA, No17 14 μA, No14 4 μA, No4 2 μA. We reconnect No5 and find 100 μA flowing in. We do the same with No12 after running for ten minutes and see 10 μA flowing in. We connect No3, 8, and 9 rejected devices and see 300 μA, ≈1.3 μA and ≈1.3 μA flowing in to each. We leave No5 , 3, 8, and 9 charging. The remaining 5 are batch T209_4. Battery voltages 3.2-3.3 V. Total noise in 37°C water is ≤3.0 μA in 2-40 Hz, switching noise <0.6 μV. Frequency response T209.4 within ±0.2 dB.

[15-OCT-18] Charging transmitters T209.3, T209.5, T209.8, and T209.9 are together consuming 200 μA, 6 μA, 1.0 mA, and 1.0 mA respectively. T209.8 and T209.9 will not turn on. T209.3 and T209.5 turn on and produce VA = 3.1 V and 3.2 V respectively. We place these two in our faraday enclosure to run down their batteries. Poaching transmitter P207.41 has stopped. P207.45 response to 20-MΩ sweep correct, 100% reception. VA = 2.9 V.

[16-OCT-18] We dissect P207.41 after 26 days poaching. No sign of corrosion. Silicone well-adhered to epoxy, but peels off in one layer. VB = 0.15 V. Disconnect VB = 0.13 V. Connect external 2.7 V, Inactive 1.4 μA, active 38 μA, 100% reception, responser to 20-MΩ sweep correct. Diagnosis "Unidentified Drain". Dissect T209.9. VB = 2.1 V. Disconnect VB = 2.2 V. Connect external 2.7 V. Inactive 0.8 μV, ative 35 μV, 100% reception, response to 20-MΩ sweep correct. Connect 100 kΩ across battery, get 20 μA. Connect transmitter again, upon turn-on, VB drops to 1.0 V. Connect 1 kΩ and VB = 0.4 V. Diagnosis "Heat-Damaged Battery". Dissect T209.8. VB = 2.1 V. Disconnect VB = 2.2 V. Connect 100 kΩ to battery VB = 2.0 V, 1 kΩ VB = 0.3 V. Connect external 2.7 V to circuit. Inactive 0.8 μA, active 33 μA, 100% reception, response to 20-MΩ sweep correct. Diagnoisis "Heat-Damaged Battery". Poaching transmitter P207.45 100% reception, response to 20-MΩ correct, VA = 2.87 V. We have B206.193 with wrinkled silicone but otherwise okay, put it in oven to poach.

[19-OCT-18] Poaching transmitters P207.45 and B206.193 battery voltages 2.76 V and 2.70 V. Reception 100%, response to 20-MΩ sweep correct. We have batch C210.1 consisting of 12 of A3028C-AA. Frequency response C201_1. Switching noise in water at 41°C is ≤8 μV and total noise 2-80 Hz is ≤10 μV rms except for C210.7, which is 15 μV rms. The noise on C210.7 does not appear to be switching noise: there is no definite peak in the spectrum. But the noise consists of random 40-μV negative pulses. We add C206.157 (an older batch) and C210.7 to our poaching devices.

We have two sizes of Ag/AgCl electrode we purchased from A-M Systems. One is a 4-mm diameter 1-mm thick AgCl pellet with 70 mm of silver wire. The other is a 3-mm long 0.8-mm diameter AgCl pellet with 70 mm of silver wire. We solder the leads of an A3028Q transmitter as shown below.


Figure: Ag/AgCl Electrodes Soldered to Stainless Steel Leads.

We place the solder joints, silver wires, and pellets in room-temperature water. Input noise for 8-s intervals is typically 5 μV rms in 2-80 Hz. But we see movements below 2 Hz that are up to 200 μV, despite our 0.3-Hz high-pass filter.



Figure: Two Examples of Noise With Solder Joints and Ag/AgCl Electrodes In Water.

We raise the solder joints out of the water leaving only the Ag/AgCl electrodes immersed. While the water is still rocking in the beaker, we see 2 Hz waves. When the water is still, noise in 2-160 Hz is 4.0 μV rms. Variation at lower frequencies is less than 2 μV. The following is typical of all intervals we record from water with two Ag/AgCl electrodes.


Figure: Noise With Only Ag/AgCl Electrodes In Water.

If we allow the solder joints to sit just outside the water, but partly wet, we see occasional steps of up to 20 mV on the input, which appear in the A3028Q signal as a step followed by a decay and overshoot with time constant roughly 0.5 s. We cut off one of the solder joints and strip the end of the stainless steel helix. We place the steel wire in the water along with the smaller pellet electrode to act as a reference on X&minusl;. We see movements below 2 Hz of much the same size and character as when we had the two solder joints immersed.

[22-OCT-18] Poaching transmitter P207.45 has stopped. Poaching transmitters B206.193, C206.157, and C210.7 reception 100%, response to 20-MΩ sweep correct. T209.3 and T209.5 both ran for over 140 hours. We connect T209.3 and T209.5 to our charger.


Figure: A3028T-R Discharging. T209.3 failed QA and failed to provide full capacity following earlier re-charges. T209.5 passed QA.

We continue our experiments with silver chloride electrodes. We first check our Ag/AgCl and 316SS electrode pair in water, and we see the same 200-μV rumble and steps we observed before. This time we take one Ag/AgCl electrode, which is an AgCl-coated pellet connected to a silver wire, and for the second electrode we provide another silver wire. Noise in 2-160 Hz is 3.8 μV and we see no rumble or steps. We cut off the Ag/AgCl pellet, leaving two silver wires in water. We see no rumble or steps. We immerse the newer solder joint in the water along with the new silver wire and see sustained pulses and rumble.

[23-OCT-18] We have three A3028T-R, T19-T21 made for poaching. These are made with the ML621 with tabs, so there is no over-heating of the battery during assembly. Their sample rate is 128 SPS but frequency response is 0.3-160 Hz. Mass of three is 3.04 g. Volume of all three is 1.45 ml. So mass of each is 1.0 g and 0.48 ml, consistent with our current 1.0 g and 0.50 ml specification. Response to 20-MΩ 60 Hz shows beats we expect from under-sampling. Connect to charger along with T209.3 and T209.5. Total charge current 620 μA.

We prepare 200 ml of 1% saline and immerse our two silver wires, attached to A3028Q No39, but with solder joints out of the water. We see 3.9 μV rms noise in 2-80 Hz. Rumble is less than 20 μV in 8-s intervals and there are no steps. We drop the entire transmitter in the saltwater, seal the jar, and place in our oven at 60°C.

Poaching transmitters B206.193, C206.157, and C210.7 reception 100%, battery voltages 2.71, 2.78, and 2.79 V respectively.

[24-OCT-18] Poaching transmitters B206.193, C206.157, and C210.7 reception 100%. Five charging A3028T-R transmitters drawing 150 μA total from 4.2 V charge voltage with 1 kΩ series resistors.

[25-OCT-18] Our five charging A3028T-R are consuming 53.5 μA. We remove them one by one. The final charge currents are 30 μA for T209.5, 3 μA for T21, 11 μA for T209.3, 4.5 μA for T20, and 5.4 μA for T19. We turn them all on and put them in our FE3AS to run their batteries down. Poaching transmitters B206.193, C206.157, and C210.7 reception 100%.

[26-OCT-18] Poaching transmitters B206.193, C206.157, and C210.7 reception 100%. Battery voltage and noise in 2-160 Hz are (id V uVrms): 7 2.78 5.2 157 2.73 6.2 193 2.69 6.0. Response to 20-MΩ sweep correct. Dissect P207.45. Silicone and epoxy in perfect condition. VB = 0.4 V. Disconnect VB = 0.4 V. Connect external 3.0 V. Active 31 μA, inactive 0.8 μA. This device ran for 800 hours. If we assume 32 μA, the CR1025 battery delivered 26 mA-hr. According to data sheets for MAX2624 and LC1865, current consumption at 60°C should be roughly 10% higher than at 20°C. We immerse the transmitter circuit in water from 18-75°C and obtain this relationship. Diagnosis "Full Life".

[29-OCT-18] Poaching transmitters B206.193, C206.157, and C210.7 reception 100%.

[30-OCT-18] Poaching transmitters B206.193, C206.157, and C210.7 reception 100%, response to 20-MΩ sweep correct. After a week in saltwater at 60°C, our A3028Q's silver wires are untarnished, but our solder joints are covered with black and gray residue. We test our two silver wires with their tips in the 1% saline. We see rumble of order 100 μV in each 8-s interval, of which here is a typical example. We solder a new silver wire with an AgCl pellet on the end to our blue lead. Rumble <20 μV in 8-s intervals, no steps. Cut off AgCl pellet leaving fresh silver wire on the blue lead and old silver wire on the red lead. We see rumble up to 100 μV in each 8-s interval, no steps, a typical interval here. We solder an AgCl pellet to the end of our old silver wire. Now we have a new AgCl pellet and a new silver wire in the saltwater. We see rumble up to 100 μV, typical interval here. Even after twenty minutes we are still seeing rumble up to 200 μV, but no steps.

NOV-18

[02-NOV-18] We have batch E210.17, consisting of 11 of A3028E-AA. Frequency response E210_17 within ±0.6 dB. Noise in 37°C water ≤10 μV rms except E210.25, which shows noise 13 μV. Switching noise <3 μV amplitude for all. Set aside E210.25 to poach.


Figure: A3028T-R Discharging. Solid lines are run one, dashed lines are run two. T19-21 batteries with tabs soldered to circuit board, these are their first and second discharges. T209.3 and T209.5 without tabs, soldered directly to circuit board and a wire. These are the fifth and sixth discharges for T209.3, and the third and fourth discharges of T209.5.

The above plot suggests that soldering directly to a ML621 manganese-lithium battery reduces both the operating voltage and the capacity of the battery. We connect all five batteries to our charger. Total current 900 μA. Poaching transmitters B206.193, C206.157, and C210.7 reception 100%, now joined by E210.25.

[05-NOV-18] Our five A3028T1-R have been charging for 60 hours. Total charge current is now 88 μA, down from 900 μA at start. Individual charge currents are T209.3 30 μA, T209.5 27 μA, T19 11 μA, T20 11 μA, T21 9 μA. The final charge current of a healthy ML621 is ≈10 μA. The current passes through two BAS116LPH4 diodes. Their combined voltage drop will be 1.1 V. With 4.2-V charging voltage, the voltage across the 1 kΩ resistor and battery combined will be 3.1 V. [We later discover that our charging voltage is only 4.1 V when the power supply meter shows 4.2 V, so charge voltage this time was 4.1 V.] We turn on all five transmitters and put them back in our cage. Poaching transmitters B206.193, C206.157, C210.7, and E210.25 100% reception, response to 20-MΩ sweep correct. Channel number, battery voltage (V) and noise (μV rms 2-160 Hz) are: 7 2.71 7.1 25 2.69 14.6 157 2.68 7.9 193 2.52 6.2.

[06-NOV-18] Poaching transmitters B206.193, C206.157, C210.7, and E210.25 100% reception, channel number, battery voltage (V) and noise (μV rms 2-160 Hz) are: 7 2.76 4.7 25 2.79 5.4 157 2.73 6.1 193 2.40 7.0.

[09-NOV-18] Poaching transmitters C206.157, C210.7, and E210.25 100% reception, response to 20-MΩ sweep correct. B206.193 has stopped after 24 days poaching. Diagnosis "Full Life". We have batch E210_27 consisting of eleven A3028E-AA. Frequency response E210_27 within ±0.5 dB. Switching noise ≤4 μV, total noise 2-160 Hz < 12 μV rms.

[12-NOV-18] Poaching transmitters C210.7, and E210.25, C206.157, 100% reception, VA = 2.72 V, 2.81 V, and 2.63 V. Our five A3028T1-R have discharged their batteries. T21 is still running, but battery voltage is 2.28 V. We connect 19-21 to our charger. The devices are initially active when we connect charging voltage, so we turn them off. Total charge current 650 μA.

[13-NOV-18] Three charging A30238T-R drawing 110 μA today. Poaching transmitters C210.7, and E210.25, C206.157, 100% reception, response to 20-MΩ sweep correct. We have an A3028U DC-160 Hz transmitter and a beaker of 1% saline. Start with Ag/AgCl electrode and its solder joint to a silver extension wire for C, and a silver wire on X. The tips of the stainless steel leads from C and X are out of the water, as is the transmitter body. We start recording M1542138183.ndf. We get this overview from 1000-1500 s. At time 1600 s we raise the solder joint in the C electrode above the water. We now have only a silver wire tip and an Ag/AgCl pellet with its attached silver wire within the saline. We get this from 1700-2200 s. From 2330-2445 s we are removing the Ag/AgCl pellet, scraping the silver wires, cutting off their tips, and replacing in saline, so we have two silver wires in water with no solder joints immersed. We get this from 3100-3600 s.

[15-NOV-18] Three charging A3028T-R drawing 15 μA today. But we note that the charging voltage is 4.1 V. We turn up to 4.2 V and see 45 μA. We check charge voltage with multimeter and get 4.21 V. Poaching transmitters C210.7, and E210.25, C206.157, 100% reception, response to 20-MΩ sweep correct.

[16-NOV-17] Three charging transmitter T19-21 consume 5 μA but we find that the charging voltage has dropped to 4.1 V. Increase to 4.2 V and see 35 μA. Remove from charger, turn on, place in beaker of water in faraday enclosure to discharge. Meanwhile, we have T209.19-22 encapsulated. Response to 20-MΩ sweep correct, noise ≤5 μV. We place on charger. Total input current 747 μA. Leave to charge for the weekend. Poaching transmitters C210.7, and E210.25, C206.157, 100% reception, battery voltages 2.70 V, 2.81 V, and 2.54 V respectively. We record from our A3028U 0-160 Hz transmitter with two silver wires in saline for 4500 s. We obtain this plot.

[19-NOV-18] Poaching transmitter C206.157 has stopped. This device sat on the shelf for four months, consuming 4.3 mAhr of its 48 mA-hr battery. It then ran for 820 hrs. Diagnosis "Full Life". C210.7 and E210.25 reception 100%, response to 20-MΩ sweep correct. Battery voltages 2.63 V and 2.81 V respectively.

[20-NOV-18] We have batch C210_41 consisting of 14 of A3028C-CC. Frequency response C210_41. Switching noise in 37°C water is ≤5 μV for all but 43, 45, and 56, which are 5-8 μV. Total noise is ≤10 μV rms in 2-80 Hz. Holding 43 and 56 for poaching. We have batch T209_19 consisting of four A3028T1-R. Final charge currents from 4.2 V supply through 1 kΩ were 5-6 μA. Frequency response T209_19. In 37°C water we have ID, reception (%), VBAT (V), and 1-40 Hz noise (uV rms): 19 100.00 3.22 2.7 20 100.00 3.27 3.0 21 100.00 3.28 2.8 22 100.00 3.30 3.0. So noise is ≤3 μV. Poaching transmitters C210.7, E210.25, C210.43, C210.53 100% reception.


Figure: A3028T-R Discharging. All devices made without soldering directly to battery. First charge with 4.2 V. Second with 4.1 V. Third with 4.2 V. Fourth with 4.3 V.

[26-NOV-18] Devices T19-21, A3028T-R, now discharged, as shown above. Connect to 4.3 V to re-charge. Total current 800 μA. Poaching transmitters E210.25, C210.43, C210.53 100% reception, response to 20-MΩ sweep correct. C210.7 has stopped after 41 days, diagnosis "Full Life".

[27-NOV-18] Devices T19-21, A3028T-R, charging with 4.3 V, total current 170 μA. Poaching transmitters E210.25, C210.43, C210.56 ID, reception, VBAT, and rms noise uV: 25 99.85 2.77 4.6 43 100.00 2.70 11.3 56 97.46 2.68 10.2. We solder two teflon-insluted 125-μm diameter 316SS leads to U204.68 and two Ag/AgCl pellet electrodes to U204.69, both 512 SPS DC-160 Hz transitters. We fasten the transmitters outside a beaker of 1% saline, their leads passign over the rim of the beaker and down into the fluid. None of the leads are touching one another. Only the tips of the stainless steel leads are in the water. We place in our faraday enclosure and start continuous recording at 12 pm.

[28-NOV-18] Poaching transmitters E210.25, C210.43, C210.56 ID, reception 100%. Devices T19-21, A3028T-R, charging with 4.3 V, total current 60 μA. Remove from charger, each was taking 20 μA. The BAS116LPH4 drops 0.57 V at 20 μA, so batteries are getting 4.3−2×0.57 = 3.16 V through 1 kΩ. Remove U204.68 and 69 from faraday enclosure and turn off. Turn on T19-21 and place in faraday enclosure to monitor discharge. We analyze U204.68 and 69 twenty-two hour recording, extracting all events with power more than twice the average. We obtain thirteen events, all on channel 68. Nine are like the picture below.


Figure: Vibration Artifact of Steel Wire Tips in Saline.

Two are more vigorous oscillations that occur when we open the cage to remove the transmitters, see here. Two are glitches.

[30-NOV-18] We have batch A210.57 consisting of four A3028A-CCC. Gain versus frequency A210_57 within 0.2 dB. Switching noise in 45°C water is ≤1 μV. Total noise 2-160 Hz ≤10 μV after scrubbing solder joints and allowing ten minutes to settle. Poaching transmitters E210.25, C210.43, C210.53 frequency response here is correct.

DEC-18

[04-DEC-18] Poaching transmitters E210.25, C210.43, C210.56 reception 100% response to 20-MΩ sweep correct.

[07-DEC-18] Connect T19-21 A3028T1-R to recharger, current is 1 mA at first, 700 μA after an hour. Poaching transmitters E210.25, C210.43, C210.56 frequency response correct, reception 100%.

[10-DEC-18] Devices T19-21 A3028T1-R are drawing 35 μA from charger. Disconnect, turn on, and add to poaching jar. Poaching transmitters T19, T20, T21, E210.25, C210.43, C210.56 response to 20-MΩ sweep correct, reception 100%.

[11-DEC-18] Poaching transmitters T19, T20, T21, E210.25, C210.43, C210.56 100% reception. Receive 7 of A3028D-DDA returned from ION after three implantations and a total of six months implanted, but only 240 hours running, according to the records of the implanter. Examine D208.171. Silicone is intact but cloudy. Some components visible through silicone and epoxy on top side of circuit board. No breeches in silicone, antenna insulation intact, leads in good condition. Dissect. Silicone adhered well to epoxy. No sign of epoxy peeling away from components where the coating is thin. VB = 0.0 V. Disconnect, VB = 0.6 V. Connect external 2.6 V. Active current 146 &uA;. Leave for ten minutes, active current now 1.6 mA. Inactive 1.5 mA. Remove C2. Burning epoxy has a vinegar smell. Active current 145 μA. Inactive 1.4 μA. Response to 20-MΩ sweep correct. Diagnosis "Corroded Capacitor". Examine D208.173. As 171 including vinegar smell. Dissect. VB = 0.6 V. Disconnect, VB = 0.6 V. Connect external 2.6 V. Active 145 μA for a few minutes, then increasing to 2 mA. Inactive 2 mA. Remove C2 and C19, no change. Remove C20, active 146 μA, inactive 2.0 μA. Response to 20-MΩ sweep correct, but 173 is 2000 counts above 172. Diagnosis "Corroded Capacitor". Examine D208.163. As 171, including vinegar smell. Dissect. VB = 0.3 V. Disconnect, VB = 0.6 V. Connect externl 2.6 V. Inactive 40 μA. Clean and dry, inactive 75 μA. After a few minutes, inactive 115 μA, active 263 μA. Remove C2, active 152 μA. Response to 20-MΩ sweep correct on Y, 6 dB too low at all frequencies on X. Response to 50-Ω sweep correct on Y, 6 dB too low at 130 Hz on X. Active current now 147 μA. Examine D208.157. As 171, but do not notic vinegar smell. VB = 0.6 V. Disconnect 1.2 V. Active 15 mA. Remove C2, C19, C20 no change. Remove U3, inactive 3.5 μA. Short U3-4 to U3-6. Connect power wrong way around, current 150 mA. Connect the right way around, current 100 mA. Remove C1, C3 no change. Diagnosis "Corrosion Short".

[13-DEC-18] Poaching transmitters T19, T20, T21, E210.25, C210.43, C210.56 response to 20-MΩ sweep correct. Note poor reception from T19-21 in 60°C water in faraday enclosure when first removed from oven. After ten minutes, water has cooled to 45°C, reception is 100% from all.

[14-DEC-18] Dissect 208.179. Many bubbles in the epoxy surface over the battery. Cloudy patches under the silicone coating of the circuit. The edge of U5 is visible. VB = 1 V. Disconnect VB = 1.2 V. Connect external 2.6 V. Active 145 μA, reception 100%. Inactive 1.2 μA. Activate 145 μA. Reception 100%. Dissect D208.167. VB = 0.8 V. Disconnect VB = 1.1 V. Connect external 2.6 V. Active 300 &muA; Reception 100%. Increasing current over next minute to 750 μA. Inactive 600 μA. Remove C2. Inactive 1.3 μA. Active 153 μA. Dissect D208.161. VB = 0.5 V. Disconnect VB = 0.2 V. Inactive 2.6 μA. Active 150 μA. Reception 100%. Leave D208.167 (without C2), D208.179, D208.161 inactive and attached to 2.6 V through 1 kΩ. Return three hours later and D208.179 is consuming 1 mA when active, dropping back to 144 μA. Switch on and off a few times and get inactive 900 μA, active 1.05 mA. Remove C2. Resistance of C2 > 2 MΩ. Active 144 μA, inactive 2 μA, switching on and off ten times no aberration. Response to 20-MΩ sweep correct for 179, 161, and 167 correct. Of the seven returned, six show evidence of corrosion. Of these five recovered after removing one of the capacitors C2, C19, or C20. Diagnosis: corroded capacitor failure in at least 5 of 7. Given that these devices were implanted for roughly 150 days each, inactive for 90% of the time, the voltage-induced corrosion occurred only in the capacitors connected directly across the battery.

[14-DEC-18] Poaching transmitters T19, T20, T21 intermittent reception in air, E210.25, C210.43, C210.56 100% at 7 pm.

[18-DEC-18] Poaching transmitters T19, T20, and T21 have stopped. Connect to charger, they draw 1.0 mA together. Diagnosis "Full Life". After three hours we disconnect from charger and measure frequency response: T19 correct, T20 too high at 80 Hz, T21 oscillating at 40 Hz. Poaching transmitters E210.25, C210.56 response to 20-MΩ sweep correct, C210.43 response 6 dB too high at 40 Hz, 6 dB too low at 80 Hz for 20 MΩ source, but correct for 100-kΩ source. At 20°C in water we have ID, VBAT (V), Noise (uV): 25 2.69 14.9 43 2.48 6.5 56 2.15 8.7. We have batch D208.185 consisting of four A3028D-DDA. Scrup solder joints on pins and place in 40°C water. Noise is <12 μV, switching noise <3 μV. Frequency response D208_185 within ±0.3 dB. We add D208.189 and D208.193 to poach at 60°C inactive, to test inactive implant corrosion resistance.

[20-DEC-18] We have batch P207.73 consisting of eleven A3028P1-AA. Frequency response P207_73 within ±0.45 dB. Noise in 1-40 Hz <4 μV, switching noise <1 μV. Hold back P207.73 for poaching. Poaching transmitters E210.25, C210.43, C210.56, D208.189, and D208.193 reception 100%. Response to 20-MΩ sweep correct for all, except C210.43 gain 6 dB too high at 40 Hz and 6 dB too high at 80 Hz, and for twenty seconds sustains its own oscillations at 40 Hz with leads open circuit. Similar problems with 100-kΩ source and 50-Ω source. Gain is too great at 40 Hz.

[21-DEC-18] Poaching transmitter C210.56 has stopped. C210.43 reception 100%, VA = 2.17 V, 20-MΩ sweep 6 dB too high at 40 Hz, 6 dB too low at 80 Hz. E210.25 100%, sweep correct. D208.189 and D208.193 100%, sweep correct. Recharging T19-T21 together draw 40 μA from 4.3V through individual 1-kΩ resistors. Turn them on. Reception 100%, sweep correct for all three VA = 3.3-3.4 V. These have 0.3-80 Hz filters but only 128 SPS so we are able to see aliasing clearly with frequencies 50-70 Hz. Add P207.73 to poach. Dissect C210.56. VB = 0.5 V. Encapsulation in perfect condition. Good adhesion of silicone. Disconnect, VB = 0.4 V. Connect external 2.6 V. Active 52 μA, reception 100%, inactive 1.3 μA. At 60°C its current consumption would be 10% higher because of the effect of temperature upon the circuit and 5% higher because the battery voltage increases, so a total of 15% hihgher makes60 μA for 800 hr. This device ran for 744 hours at 60°C. It's battery voltage on 12DEC18 was 2.15 V. After an hour, current consumption at room temperature is 51 μA. Diagnosis "Unidentified Drain".

[24-DEC-18] Poaching transmitter C210.43 response to 20-MΩ sweep correct when freshly removed from hot water is correct. As it cools, oscillations at 40 Hz develope, replace in hot water, oscillations stop after thirty seconds. Reception 100%, VA = 2.50 V. Transmitters T19, T20, T21 in hot water reception 100%, noise ≤10 μV, VB ≈2.6 V. When we allow to cool to room temperature in air, T21 starts oscillating at around 40 Hz. We return to hot water and oscillations stop in thirty seconds. We place T19-T20 in the oven to bake for half an hour. Now all three provide correct response to 20-MΩ sweep, but after five minutes at room temperature, T21 starts oscillating at around 60 Hz. Place in the oven for another half-hour. Upon removel, all three provide correct response to 20-MΩ. Drop in 20°C water. After five minutes, no oscillations. Remove and find sweep response correct. Return to poach. P207.73, E210.25, D208.189 and D208.193 reception 100%, response to 20-MΩ sweep correct. Switch off D208.189 and D208.193.

[26-DEC-18] Poaching transmitters reception 100% except C210.43, which has stopped. Diagnosis "Full Life". For 1-s intervals ID, VA (V), Noise (uV rms 1-40 Hz): 19 2.48 4.2 20 2.51 14.1 21 2.52 3.3 25 2.73 8.3 73 3.02 3.4 189 2.70 6.6 190 2.72 6.5 193 2.69 15.3 194 2.67 12.8.

[27-DEC-18] Poaching transmitters immediately after removal from oven, 1-s intervals ID, VA (V), Noise (uV rms 1-40 Hz): 19 2.42 3.2 20 2.46 4.1 21 2.46 4.1 25 2.77 3.6 73 3.02 2.9. Turn on D208.189 and D208.193, reception 100%, response to 20-MΩ sweep correct. Remove each of the remaining one by one from water. T19, T20 sweep correct. T21 sweep correct for a few seconds, then 2-Hz square wave starts up. P207.73 and E210.25 sweep correct.

[28-DEC-18] Poaching transmitters T19 and T20 have stopped, but T21 still running with VA = 2.19 V. Diagnosis "Full Life". Remove, connect all three to 4.3 V with their own 1-kΩ resistor and see total current 0.9 mA. For remaining devices reception is 100% and in 1-s intervals we have ID, VA (V), Noise (uV rms 1-40 Hz): 25 2.73 8.3 73 3.02 3.2 189 2.77 17.2 190 2.78 15.0 193 2.74 5.3 194 2.74 7.1.

[31-DEC-18] Poaching transmitters P207.73, E210.25, D208.189, D208.193 response to 20-MΩ sweep correct, reception 100%. Charging current for T19, T20, T21 is 38 μA. Sweep response correct for T19 and T20, but T21 has unstable baseline. Put in oven to dry for an hour, then add to poaching water in inactive state, like D208.189 and D208.193.

2019

JAN-19

[08-JAN-19] Poaching transmitters P207.73, E210.25, D208.189, D208.193, T19, T20, T21 reception 100%. T19 generating 1-Hz square wave, no response to 20-MΩ sweep. T20 and T21 rumble of around 100 μV, correct response to 20-MΩ sweep. P207.73, E210.25, D208.189, D208.193 correct response to 20-MΩ sweep.

[09-JAN-19] We have batch K207.55 consisting of 12 of A3027K-AA 0.3-40 Hz, 128 SPS, 1.3 ml. Frequency response K207_55 within ±0.7 dB. Noise 1-40 Hzz in 37°C water <7 μV, switching noise ≤ 5 μV except for K207.65 and K207.68, which have 1-40 Hz noise 8 μV and switching noise 6 μV, see spectrum. All are okay to ship, but hold back these last two for poaching.

[10-JAN-19] Add K207.65 and K207.68 to poach. ID, VA (V), and 1-40 Hz noise (uV): 25 2.72 9.4 65 2.76 6.3 68 2.87 3.8 73 3.18 2.9 189 2.76 9.0 190 2.76 26.8 193 2.72 8.0 194 2.72 20.2. T19-21 turn on and transmit 100%.

[11-JAN-19] Poaching transmitters 100% reception.

[14-JAN-19] Poaching transmitters 100% reception except for P207.73, which has stopped. K207.65 and K207.68 response to 20-MΩ sweep correct.

[15-JAN-19] Add P207.105 to 60°C poach. This device had its red lead replaced after epoxy encapsulation, so we won't expect its amplifier to resist corrosion, but we can test it for battery drain. Poaching transmitters K207.65, K207.68, E210.25, D208.193, P207.105 100% reception and response to 20-MΩ sweep correct. D208.189, T19 100% reception and response to 100-kΩ sweep correct. T21 100% reception, response to 100-kΩ sweep a 1-Hz full-scale oscillation plus response to sweep. T20 won't turn on. Connect to 4.3V through 1 kΩ see 300 μA flow in. After twenty minutes, 180 μA. Now get 100% reception and response to 100-kΩ sweep is a 1-Hz square wave. Re-connect to charger. Dissect P207.73. VB = 0.5 V. Disconnect, VB = 0.6 V. Connect external 2.7 V. Inactive 0.8 μA. Active 31 μA.

We begin another search for slow artifacts with our two DC-160 Hz single-channel mouse transmitters. We equip U204.68 with two bare wire electrodes fastened to a simulated animal skull made of dental cement with 00-80 screws. We place in a covered petri dish filled with 1% saline. We equip U204.69 with two crimp electrodes. One consists of 3 mm of steel tube crushed around the bare spring. The other consists of 3 mm of steel tube crushed around the spring and a 125-μm steel wire.


Figure: Electrodes in Saline. Left: Crimped electrodes, one stainless steel wire crimped to steel spring, one crimp on steel spring only. Right: Bare wire and screw electrodes in dental cement.

We place in faraday enclosure and start recording. We are looking for artifacts like the one shown below, recorded with an A3028U-AA two-channel DC-160 Hz device.


Figure: Slow Artifact Recorded by Two-Channel Transmitter On Mouse Skull. Two bare wires are held on skull by two screws, one above motor cortex, the other above visual cortex.

[18-JAN-19] We have batch P207.87 consisting of eleven A3028P1-AA. Frequency response P207_87, except omit P207.114 because it's bandwidth is 0.3-80 Hz, when it should be 0.3-40 Hz. Noise 1-40 Hz <4 μV, switching noise <1 μV. Keeping P207.114 for poaching, inactive test starting today. Poaching transmitters K207.65, K207.68, E210.25, P207.105, D208.193 100% reception and response to 20-MΩ sweep correct. D208.189 100% reception and response to 100-kΩ sweep correct. T19 and T21 100% reception. T20 we have re-charged. Charge current now 2.5 μA. Response to 20-MΩ sweep correct. Turn on and place in faraday enclosure at 13:40 18-JAN-19. We return to our DC transmitters and produce a write-up here.

[22-JAN-19] Poaching transmitters K207.65, K207.68, E210.25, P207.105, D208.189, D208.193, P207.114 100% reception and response to 100-kΩ sweep correct. T19 and T21 100% reception. We have batch B205.21 consisting of ten of A3028B-DD, but we note that they don't have their pins soldered on yet. Frequency response B205_21 within ±0.2 dB. Noise 2-160 Hz in 40°C water ≤8.0 μV except B205.28 is 14 μV, switching noise ≤3 μV.

[23-JAN-19] Poaching transmitters K207.65, K207.68, E210.25, P207.105 100% reception. Don't turn on the inactive test devices.

[24-JAN-19] We have batch D208_195 consisting of ten A3028D-DDA. Frequency response D208_195 within ±0.3 dB. Switching noise in 37°C water <2 μV, total noise 1-160 Hz after scrubbing pins ≤11 μV. Poaching transmitters K207.65, K207.68, E210.25, P207.105 100% reception. Don't turn on the inactive test devices.

[25-JAN-19] T20 ran its battery down in 122 hours. Recharging now with 200 μA now. Poaching transmitters K207.65, K207.68, E210.25, P207.114, D208.189, D208.193 100% reception, response to 100-kΩ sweep correct. P207.105 response to 100-kΩ sweep 3 dB too low at 40 Hz, reception 100%, generates square wave in water. Recall that this device had its X-lead replaced by burning epoxy, so we expect early failure of its amplifier. T19 and T21 reception 100%, both generating 1-Hz square wave in water.

[29-JAN-19] Poaching transmitters K207.65, K207.68, E210.25, P207.114, D208.189, D208.193, P207.105 100% reception, response to 100-kΩ sweep correct. Note that P207.105 has recovered since previous test. T19 and T21 reception 100%, both generating 1-Hz square wave in water. T20 is drawing 8 μA from charger. Charging voltage 4.37 V. Turn on and place in water in faraday enclosure to exhaust battery.

[31-JAN-19] Poaching transmitters T19, T21, K207.65, K207.68, E210.25, P207.105, P207.114, D208.189, D208.193 100% reception.

FEB-19

[01-FEB-19] We have two A3028D-DDA, D208.219 and D208.221. Frequency response D208_219 within ±0.7 dB. Switching noise in 37°C water is <2 μV, 2-160 Hz noise <12 μV after much scrubbing of the solder joints. Poaching transmitter E210.25 has stopped. K207.65, K207.68, P207.114, D208.189, D208.193, P207.105 100% reception and correct response to 100-kΩ sweep. Dissect E210.25. VB = 0.6 V. Disconnect, VB = 2.7 V. Connect external 2.7 V. Inactive 3.1 mA. Active 3.2 mA, 100% reception. Heat up C5 and C2 with 370°C iron. Active 78 μA. Diagnosis "Corroded Capacitor". We have two A3028GV1 circuit boards from B78082. When programmed as A3028B they consume 100 μA, higher than the typical 78 μA. We disable the logic chip functions and current is 50 μ. We remove logic chip and tie U9-4 to U9-3 to disable the VCO. Active current 300 μA for both. We connect U7-1 to U7-10 to send U7 to sleep. But current is still 300 μA in both, and R4 is dropping 0.3 V. We connect U7-6,7,8 to U10-9 but still get 300 μA. Remove U7 and get 10 μA from both, which is about right for what we have left on the board.

[04-FEB-19] Poaching transmitters T19, T21, K207.65, K207.68, P207.105, P207.114, D208.189, D208.193 100% reception and correct response to 100-kΩ sweep. T20 has stopped. It ran for 130 hours. Attach to 4.4 V through 1.0 kΩ and it draws 600 μA at first, then 150 μA after twenty minutes.

[05-FEB-19] We receive four A3028T1-R, T209.1, 2, 4, and 10. These were charged and shipped in September and October. T209.1 and T209.10 turn on with VA = 2.19 V and 2.23 V respectively. T209.2 and T209.4 won't turn on. Connect to 4.4-V 1-kΩ charger. Charge currents 170, 40, 270, and 140 μA respectively. We remove No2 and find it turns on for a few minutes. Re-connect to charger and see only 40 μA current. Leave them all connected, along with T20, which now draws 50 μA. Poaching transmitters T19, T21, K207.65, K207.68, P207.105, P207.114, D208.189, D208.193, 100% reception.

We have another A3028GV1 from B78082 with active current consumption 100 μA when it should be 80 μA. Remove U9, the VCO, and current drops to 73 μA. Remove U7 and current is 66 μA. Remove U6, 62 μA. Remove U5 61 μA. Reprogram U8 to eliminate state machines and ring oscillator, 39 μA. Remove U10, 34 μA. Remove U8, 2.5 μA. Turn off with magnet, 1.4 μA.

We have batch A3028S_67 consisting of fifteen of A3028S2A-AA before encapsulation. These devices have bandwidth DC-80 Hz, 256 SPS, and dynamic range ±100 mV. We apply 200 mVpp through 50-Ω at 10 Hz to the input of S210.74 and see 14702 cnt rms. The amplifier gain is 4.8 μV/cnt. We apply 345 mVpp through 20 MΩ to the input at 10-Hz. We see 7485 cnt rms on the transmitted signal, or 102 mV pp. The input resistance is 8.4 MΩ. We apply a 0.1-Hz, 200 mVpp square wave through 50 Ω and the output stable after the steps to ±5 μV for three seconds, suggesting a time constant of at least three hours. We proceed to check the response of all circuits with a 350-mVpp, 20-MΩ, 1-Hz square wave, looking at the bounce after the steps to confirm frequency response.


Figure: Response of A3028S2Z to 350-mVpp, 20-MΩ, 1-Hz Square Wave.

Considering the response above, assuming the nominal 10-MΩ input resistance, we expect 115 mVpp on X. The nominal amplifier gain is 10.0, so 1.15 Vpp appears on the ADC input. Our battery voltage was 2.55 V, so we expect 29 k-cnt-pp. We observe 22 k-cnt-pp.

[07-FEB-19] Device T209.2 failed to re-charge: after one day its recharge current was still the same 40 μA, we place in enclosure and it runs down its battery in a few hours. Devices T209.1, 4, and 10 together consume 50 μA from the charger after two days. We place in 37°C water and get VA (V) and 2-40 Hz noise (μV rms): 3.39 5.1 3.19 6.5 3.39 2.7. Response to 20-MΩ sweep correct. Ready to return to customer. Poaching transmitters T19, T21, K207.65, K207.68, P207.105, P207.114, D208.189, D208.193 100% reception.

[11-FEB-19] Poaching transmitters K207.65, K207.68, P207.105 100% reception. Do not turn on the inactive devices.

[12-FEB-19] We observe yellow and brown staining around the BR1225 batteries we soldered to A3028PV1 circuits for A3028S2Z and subsequently encapsulated. The circular plastic seal between the terminals is deformed in these cases. We reproduce the effect on fresh batteries. With the help of acid flux and care taken to avoid touching the battery near the seal, we load three batteries onto three circuits and program then as A3028P5, current consumption 250 μA, P177, P178, P179. There is no sign of damage to the seals on these devices, but 179 has a stain between the seal and the wire joint that we cannot remove with water washing. Of our batch of 15 A3028S2Z we find that seven have damaged seals but batteries still deliver ≈2.8 V, one has a damaged seal and its battery is drained, and seven have no sign of damage on their seals and deliver ≈2.8 V.


Figure: BR1225 Discharge from Damaged Seal After Overheating. We encapsulated the battery with epoxy after we soldered it to the board, and we can see the discharge from the battery forced its way through, and mixed with, the epoxy while the epoxy was curing.

We select four devices with damaged seals that still run: S210.70, 72, 73, and 78. We re-program as S5 and place them in an enclosure to run down. Of the seven that show no sign of seal failure, we take S210.68 and re-program as S5 and place in enclosure to run down. We remove the battery from S210.67 and find quiescent current 51 μA. We clean up the epoxy and solder a new battery to the circuit board.


Figure: A3028S2Z with New BR1225 Battery Loaded. The circuit and original battery were encapsulated in epoxy only. We removed the original battery and soldered a new one in its place. This battery shows no sign of damage in the circular plastic seal between the battery terminals.

Poaching transmitters T19, T21, K207.65, P207.105, P207.114, D208.189, D208.193, 100% reception. K207.68 has stopped and will not turn on. K207.65, P207.114, D208.189, D208.193 correct response to 100-kΩ sweep. Don't test the others. Dissect K207.68. VB = 1.0 V. Disconnect 1.6 V. Connect external 2.7 V. Inactive 1.6 μA. Active 36 μA. Reception 100%. Diagnosis "Unidentified Drain". Device T209.2, which failed to re-charge, we dissect. We remove the battery and find active current 32 μA.


Figure: Battery Voltage Versus Time for Soldered BR1225 with 250 μA Quiescent Current. Devices 70, 72, 73, 78 have visible discharge from their soldered batteries. Devices 68, 177, 178, and 179 have no visible discharge and no visible deformation of their plastic ring seals, but 179 has a stain beside the wire solder joint that we cannot remove.

The four devices with visible battery damage expired within 64 hours. The remainder are still running well. The nominal battery life at 250 μA is 190 hrs.

[18-FEB-19] Poaching transmitter K207.65, D208.189, D208.193 100% reception, response to 100-kΩ sweep correct. T19, T21 100% reception. P207.114 100% reception but generates its own 60-Hz oscillation even in water. P207.105 has stopped. Place T20 back in enclosure after five days charging.

[19-FEB-19] Of our eight A3028S5Z circuits, only three are still running. The four with visible battery discharge all failed within 65 hr. The one with a stain between the seal and the wire joint failed after 156 hr. The other three are running after 170 hr. We see the battery voltage being affected by temperature, which varies from 10-20°C in our office.


Figure: BR1225 Battery Capacity versus Load Current and Temperature.

Looking at the figure above, the capacity of the batteries in our test, with 250-μA load and 12°C average temperature, is around 42 mA-hr, instead of the usual 48 mA-hr we assume for implanted BR1225, making the nominal operating life 168 hr.

We have batch T209_23 consisting of four A3028T1-R-AA. In 37°C water we have ID, VB (V), and noise 2-40 Hz (uV rms) is: 23 2.64 3.0 24 2.63 3.7 25 2.63 4.5 26 2.64 3.9. No sign of switching noise <0.8 μV. Frequency respose T209_23 correct. Connect to 4.4-V 1-kΩ charger and see total current 1 mA evently distributed. We have batch B211_1 consisting of eleven A3028B-AA. Frequency response B211_1 within ±0.4 dB. Noise 2-160 Hz in 37°C water is ≤11 μV, switching noise ≤4 μV.

Dissect P207.5. Yellow corrosion around base of red lead, where we re-soldered. Remove silicone and stain of corrosion lies in a trail from the joint to the negative battery wire which appears to have a spot of bare metal. VB = 0 V. Disconnect, VB = 0V. Connect external 2.7 V, Active 33 μA, inactive 0.8 μA. Diagnosis "Unidentified Drain". Poaching transmitter K207.65, D208.189, D208.193 100% reception. K207.65 response to 100-kΩ sweep correct. T19, T21 100% reception. P207.114 100% reception but generates oscillation.

[20-FEB-19] Poaching transmitter K207.65 100% reception but VA = 2.18 V. Batch T209_23 four A3028T1-R-AA still charging, combined current 55 μA.

[20-FEB-19] Batch T209_23 four A3028T1-R-AA still charging, combined current 25 μA. Remove from charger, turn on and place in 20°C water, get ID, VBAT (V), and noise 2-40 Hz (μV rms): 23 3.43 2.8 24 3.49 2.7 25 3.47 2.9 26 3.46 2.9. Ship T209.23. Keep the other three running in water in faraday enclosure. Poaching transmitter K207.65 has stopped. Inactive poaching transmitters D208.189, D208.193, P207.114, T19, and T21 100% reception. Dissect K207.65. Silicon and epoxy inaffected by 42-day poach. VB = 0.8 V. Disconnect, VB = 0.8 V. Connect external 2.7 V. Active 38 μA, inactive 4.0 μA. Increase voltage to 4.1 V, inactive current 15 μA. Active current 48 μA. Reception 100%. Drop voltage to 2.7 V and inactive current is now 1.6 μA. Diagnosis "Corrosion Short". We have 5 of A3028S2Z-AA upon which we have replaced the batteries because of discharge visible through the epoxy. We have coated them in silicone. We turn on and place in warm water. We get ID, VBAT (V), and noise 2-80 Hz (μV rms): 67 2.97 3.7 70 2.73 4.3 72 2.75 3.1 73 2.72 5.0 78 2.70 3.8. The No67 battery voltage 2.97 V is sustained. We leave to soak in water.

[25-FEB-19] We have batch L210_85 consisting of 12 of A3028L-DDA. Of thse, one, L210.89, does not turn on. Frequency response L210_85 within ±0.7 dB. Noise in 37°C water 2-320 Hz ≤14 μV, switcing noise <1 μV.

[26-FEB-19] Dissect L210.89. VB = 0.3V. Disconnect VB = 2.2 V. Connect external 2.7 V. Active 14.83 mA, inactive 14.82 mA. Lever circuit board off batter but break off most of the parts on the top side of the board. There is a cavity over the logic chip. We cannot determine the source of the high current drain.

[28-FEB-19] Inactive poaching transmitters D208.189, D208.193, P207.114, T19, and T21 100% reception.

MAR-19

[01-MAR-19] We have batch S210_67 consisting of 15 of A3028S2Z-AA with lead lengths 35 mm or 100 mm. We apply 0.25 Hz, 160-mVpp 20-MΩ sweep. We see 12.4 kcnt-pp amplitude on the input. With 10-MΩ input impedance we expect the voltage on the transmitter input to be 53 mVpp. Scale is is 4.3 μV/cnt, dynamic range 280 mV. Assuming battery voltage 2.6 V, amplifier gain appears to be 9.2 at 0.25 Hz. Gain versus frequency S210_67 within ±0.9 dB. Input noise 2-80 Hz in 37°C water is ≤ 50 μV rms with switching noise ≤34 μV. S210.68 has sample rate 2048 SPS, so must reject. S210.73 has some cloudy patches in the silicone over the battery. S210.78 has leads that are only 37 mm long.


Figure: A3028S2Z Spectrum. Scale is 10 Hz/div and 4.3 μV/div. These devices have gain ×10 rather than our usual ×100. Switching noise, which appears on the input of the sixteen-bit analog-to-digital converter (ADC), remains the same in units of ADC counts, but is ten times greater compared to the EEG signal.

Volume of 12 of A3028S2Z is 20.0 ml, including leads and antenna, so each is 0.83 ml. We adjust our specified volume down from 0.90 ml to 0.85 ml.

[05-MAR-19] Inactive poaching transmitters D208.189, D208.193, P207.114, and T21 100% reception. Gain versus frequency for D208.189 and D208.193 correct on all channels for 100-kΩ sweep. P207.114 and T21 generating their own square waves. T19 won't turn on. We add S210.67 and S210.78, both A3028S2Z, and S210.68 an A3028S5, to the poach for active test. T20 ran for 120 hours during its most recent discharge. We dissect and find active consumption is 29 μA with 2.5-V supply, inactive is 0.8 μA. Dissect T19. Inactive current 0.9 μA, active 6.0 mA. Increase supply to 4.2 V, active 2.0 mA. Drop back to 2.5 V, 1.3 mA. Diagnosis "Corroded Capacitor".

We complete discharge of three BR1225 soldered to A3028S5 circuit board, average current consumption 250 μA, and obtain this plot of battery voltage versus time. Operating live is 190 hrs, or 48 mA-hr. Nominal capacity 48 mA-hr. We complete discharge of three ML621 encapsulated in A3028T1-R-AA, average current consumption 32 μA, and obtain this plot of battery voltage versus time. Operating life is 230 hrs, or 7.4 mA-hr. Nominal capacity 5 mA-hr. Connect the three A3028T1R to charger 4.4 V in series with 1 kΩ. Current is 700 μA.

[07-MAR-19] Active poaching transmitters S210.67, S210.68, and S210.78 100% reception. Inactive poaching transmitters D208.189, D208.193, P207.114, and T21 100% reception. T21 and P207.114 producing a variety of 0.5-Hz oscillations.

[08-MAR-19] Three A3028T1R charging with current 43 μA after three days connected. Disconnect, turn on, place in enclosure and start another discharge.

[11-MAR-19] Active poaching transmitters S210.67, S210.68, and S210.78 100% reception and response to 100-kΩ sweep correct. Inactive poaching transmitters D208.189, D208.193, P207.114, and T21 100% reception.

[12-MAR-19] Active poaching transmitters S210.67, S210.68, and S210.78 100% reception.

[14-MAR-19] Active poaching transmitters S210.67, S210.68, and S210.78 100% reception. Battery voltages 2.81 V, 2.00 V, and 2.79 V respectively. After a few minutes cooling down, S210.68 stops. Noise in 67 and 78 is roughly 35 μV rms, accounting for the gain of ×10 for these A3028S2Z devices.

[15-MAR-19] Active poaching transmitters S210.67 and S210.78 100% reception. Battery voltages 2.79 V and 2.78 V respectively.

[18-MAR-19] A transmitter in quality control, B210.165, has C15 not soldered at one end. The Y amplifier produces 2.6 Vpp 180-Hz oscillation. We see 300 μV amplitude 180 Hz in the spectrum of the X input. We fix C15 and the noise on X stops. Active poaching transmitter S210.67 has stopped, and S210.78 reception is 100%, but it generates a half-scale 100-Hz oscillation.

[19-MAR-19] We have batch L210_117 consisting of fifteen A3028L-DDA. Frequency response L210_117 within ±1 dB for all thirty channels. In 37°C water, after scrubbing leads, noise 2-320 Hz ≤12 μV with switching noise <1 μV. With 20 channels at 1024 SPS we have 30 KSPS. We have two antennas and find that average reception is 70%. We remove one antenna and average reception is 69%. Loss is dominated by collisions, and collisions occur simultaneously at both antennas. Dissect S210.67. Silicone intact, but see pronounced white stains at two points around the rim of the positive battery terminal. VB = 1.9 V. Disconnect battery, connect exterior 2.6 V. Current is 2 mA at first, then drops to 50 μA after a ten seconds. Jumps up above 1.5 mA for a few seconds, returns to 49 μA. Does this again. Diagnosis "Corroded Capacitor".

Active poaching transmitter S210.78 100% reception, ≈100 Hz oscillation. Inactive poaching devices T21, P207.114 100% reception 1-Hz full-scale oscillation. Inactive poaching D208.193 100% reception and 100-kΩ sweep correct. Inactive poaching D208.189 100% and 100-kΩ sweep correct on channel 189, but 10 dB too low at 100 Hz on 190.

[22-MAR-19] Active poaching transm itter S210.78 100% reception. At first generates 125 Hz oscillation, but then settles down to quiet, and response to 100-kΩ sweep correct. Our three A3028T1-R have been charging for three days, total current is now 25 μA. We turn them on and put them in water in a faraday enclosure.

[25-MAR-19] Active poaching transm itter S210.78 100% reception generates 125 Hz oscillation. Inactive poaching devices T21, P207.114, D208.189, and D208.193 100% reception.

[26-MAR-19] We have batch B210_153 consisting of fourteen A3028B-CC. Frequency response B210_153 within ±0.5 dB. Noise 2-160 Hz is ≤10 μV rms and switching noise <3 μV except No167, which has total noise 15 μV rms and switching noise 5 μV. We set this one aside. We also have No155 noted as being left on for some time during encapsulation, so we set this one aside also. Active poaching transm itter S210.78 100% reception generates 125 Hz oscillation.

[28-MAR-19] Active poaching transmitter S210.78 100% reception generates 125 Hz oscillation.

[29-MAR-19] Active transmitter S210.78 100% reception, no oscillation, VA = 1.9 V. Inactive poaching devices T21, P207.114, D208.189, and D208.193 100% reception.

APR-19

[01-APR-19] Active transmitter S210.78 100% reception, no oscillation, VA = 1.9 V. Inactive poaching devices T21, P207.114, D208.189, and D208.193 100% reception. Yesterday we find our three discharging A3028T1-R devices have exhausted their batteries after 205 hrs. We connect to recharger and see a total of 1.5 mA. Today we see 0.5 mA. Three discharge curves are here.

[09-APR-19] Active transmitter S210.78 100% reception, no oscillation, VA = 2.7 V, response to 100-kΩ sweep correct. Inactive poaching devices P207.114, D208.189, and D208.193 100% reception. P207.114 produces square wave, D208.189, and D208.193 correct response to 100-kΩ sweep. Inactive poaching device T21 won't turn on. Start recharging, but input current only 45 μA.

[12-APR-19] Active transmitter S210.78 100% reception.

[15-APR-19] Active transmitter S210.78 has turned off. Diagnosis "Full Life". Inactive poaching devices P207.114, D208.189, and D208.193 100% reception.

[16-APR-19] Begin active poach at 60°C of A3028B B210.155 and B210.167. B210.155 we did not ship because we left it on for between one and four days by mistake. B210.167 we did not ship because it was noisy. We have B211.9 back from customer after three months on the shelf. Dissect VB = 0.1 V. Disconnect VB = 0.2 V. Apply external 2.6 V. Active 80 μA, inactive 1.3 μA. Diagnosis: "Full Life", was left on by accident.

[23-APR-19] Poaching transmitters B210.155, B210.167, D208.189, D208.193, P207.114 100% reception. Response to 100-kΩ sweep correct for D208.189 X but gain 10 dB too low on Y, correct for D208.193 X, 6 dB too high at 130 Hz for Y, correct for B210.155 and B210.167. P207.114 gives 1-Hz square wave.

[29-APR-19] We have batch C210.169 consisting of seven A3028C-CC. Frequency response C210_169 within ±0.8 dB. Noise 2-80 Hz is ≤8 μV, switching noise <4 μV.

[30-APR-19] Poaching transmitters B210.155, B210.167 100% reception.

MAY-19

[01-MAY-19] Active poaching transmitters B210.155, B210.167 100% reception, response to 100-kΩ sweep correct. Inactive poaching transmitter D208.189 100% reception, 100-kΩ sweep response 10 dB too low at 100 Hz on both channels. Inactive poaching transmitter D208.193 100% reception, 100-kΩ sweep response 10 dB too high at 100 Hz on one channel. Inactive poaching transmitter P207.114 won't turn on.

[03-MAY-19] We have batch A210.179 consisting of six A3028A-CCC transmitters. Gain versus frequenvy A210_179 within ±0.3 dB. Noise 2-160 Hz ≤10 μV rms. Switching noise ≤3 μV.

[06-MAY-19] Active poaching transmitter B210.167 100% reception, but B210.155 has stopped.

[06-MAY-19] Active poaching transmitter B210.167 100% reception, response to 100-kΩ sweep correct. Inactive poaching transmitter D208.189 100% reception, 100-kΩ sweep response 10 dB too low at 100 Hz on both channels. Same with 50-Ω sweep. Inactive poaching transmitter D208.193 100% reception, 100-kΩ sweep response 10 dB too high at 100 Hz on one channel, correct on the other. Same with 50-Ω sweep. Dissect B210.155. VB = 0.4 V. Disconnect VB = 0.4 V. Connect external 2.6 V. Inactive 1.4 μA, active 87 μA, reception 100%, response to 100-kΩ sweep correct. Expected life with 87 μA is 23 days, this transmitter ran for several days before test began, so diagnosis is "Full Life". Dissect P207.114. Remove battery and connect external 2.6 V. Inactive 1.0 μA. Active 33 μA for a minute, then jumps to 400 μA. Diagnosis "Corroded Capacitor".

[10-MAY-19] Active poaching transmitter B210.167 100% reception, response to 20-MΩ sweep correct.

[13-MAY-19] Active poaching transmitter B210.167 has stopped. Diagnosis "Full Life".

[14-MAY-19] We have four bare A3028GV1 circuit boards that show current consumption roughly 30 μA higher than usual.


Figure: Current Consumption versus Sample Rate for Faulty A3028GV1 Circuits A-D.

We remove all components except logic power supplies and logic chip from one circuit board. The current consumption of what is left is 27 μA, which is 13 μA higher than the typical current consumption of the logic chip (11 μA) plus the typical current consumption of the magnetic switch (2 μA) and flip-flop (0.5 μA).

[21-MAY-19] We have three A3028GV1 with roughly 10 μA excessive current consumption. We program them as A3028K, 128 SPS, nominal current 35 μA. They are now K209, K210, and K211, with current consumption 52.5 μA, 51.4 μA, and 48.6 μA respectively. We solder CR1220, 30-mAhr batteries to their programming extensions and place them in a Faraday enclosure. If their current consumptions remain constant, we expect their operating lives to be 570, 580, and 620 hrs respectively.

[24-MAY-19] We have batch B205_34 consisting of 11 of A3028B-DD. Frequency response B205_34 within 0.4 dB. Switching noise in 38°C water ≤4 μV amplitude, total noise 2-160 Hz ≤12 μV except for B205.37, which shows persistent rumble 2-5 Hz of 40-100 μV, despite brushing and instpecting electrode pins.

[28-MAY-19] We have batch B211_13 consisting of 12 of A3028B-AA with 55-mm leads tipped with bare-wire electrodes. Frequency response B211_13 within ±0.4 dB. Total noise 2-160 Hz in 37°C water ≤8 μV, switching noise ≤4 μV. We have B205.59 with 90-mm leads terminated with D-pins. Its total noise before scrubbing pins is 100 μV rms, after scrubbing 20 μV rms, and its switching noise is 5 μV. We set this one aside to poach.

Inactive poaching transmitters D208.189 and D208.193 100% reception. Inspect encapsulation. Original ripples in silicone remain unchanged. Label print is fading. No sign of rust. Can still see a few components through the silicone and thin layer of epoxy. Both transmitters generating 1-Hz square waves on both channels when open-circuit in air. Add to active poach B205.59 and B211.25. The latter's current consumption during quality control was 84 μA.

[31-MAY-19] Active poaching transmitters B205.59 and B211.25 100% reception.

JUN-19

[04-JUN-19] Active poaching transmitters B205.59 and B211.25 100% reception, response to 100-kΩ sweep correct. Inactive poaching transmitters D208.189 and D208.193 100% reception.

[07-JUN-19] Active poaching transmitters B205.59 and B211.25 100% reception, response to 100-kΩ sweep correct. Inactive poaching transmitters D208.189 and D208.193 100% reception.

[11-JUN-19] Active poaching transmitters B205.59 and B211.25 100% reception. The faulty A3028GV1 circuits with current consumption roughly 10 μA too high at time of quality assurance take 700 hours to run down a 30 mA-hr battery, see below. If their current consumptions had remained constant, and the capacit of the battery were 30 mAhr, we would expect their operating lives to be 570, 580, and 620 hrs respectively.


Figure: Battery Voltage versus Time for A3028GV1 with Excessive Current Consumption. Circuits K209-11, programmed 128 SPS, current ≈50 μA, 30 mA-hr battery.

[19-JUN-19] We have batch C207_116 consisting of twelve of C3028C-AA. Frequency response C207_116 ±0.8 dB. Gain is higher at 2 Hz than usual, but all are the same, and all are within ±2 dB of nominal. Noise in 37°C water is ≤6 μV 2-80 Hz, switching noise ≤3 μV. Active poaching transmitters B205.59 and B211.25 100% reception.

[21-JUN-19] Active poaching transmitter B211.25 100% reception and correct response to 100-kΩ sweep, B205.59 has stopped. Diagnosis "Full Life". Inactive poaching transmitters D208.189 and D208.193 100% reception.

[24-JUN-19] Active poaching transmitter B211.25 has stopped. Diagnosis "Full Life". Inactive poaching transmitters D208.189 and D208.193 100% reception.

JUL-19

[22-JUL-19] We have batch E200_125 consisting of 12 of A3028E-FB. Frequency response E200_125.gif within ±0.4 dB. Noise 2-160 Hz ≤12 μV, switching noise in 37°C water ≤4 μV. Inactive poaching transmitters D208.189 and D208.193 100% reception. Add E200.125 and E200.126 to active poach.

[23-JUL-19] Inactive poaching transmitters D208.189 and D208.193 100% reception. Active poaching transmitters E200.125 and E200.126 100% reception, response to 20-MΩ sweep correct.

[26-JUL-19] Inactive poaching transmitters D208.189 and D208.193 100% reception. Active poaching transmitters E200.125 and E200.126 100% reception, response to 20-MΩ sweep correct. We have batch C207_130 consisting of nine of A3028C-AA. Frequency response C207_130 within ±0.9 db. Noise 1-80 Hz ≤5 μV except No13710 μV. Switching noise <4 μV.

AUG-19

[05-AUG-19] Inactive poaching transmitters D208.189 and D208.193 100% reception. Active poaching transmitters E200.125 and E200.126 100% reception, response to 20-MΩ sweep correct.

[06-AUG-19] We have batch E212_1 consisting of eleven of A3028E-AA. Frequency response E212_1 within ±0.8 dB. Switching noise in 37°C water ≤2 μV. Total noise 1-160 Hz 5-9 μV rms.

[09-AUG-19] Inactive poaching transmitters D208.189 and D208.193 100% reception. Active poaching transmitters E200.125 and E200.126 100% reception, response to 20-MΩ sweep correct.

[12-AUG-19] We have batch A210_195 consisting of five of A3028A-CCC. Frequency response A210_195 within ±0.3 dB. Switching noise in 37°C water ≤3 μV. Total noise 1-160 Hz 6-10 μV rms. We have batch E200_139 consisting of twelve of A3028E-FB. Frequency response E200_139 within ±0.6 dB. Switching noise in 37°C water ≤3 μV. Total noise 1-160 Hz 8-12 μV rms.

[13-AUG-19] Inactive poaching transmitters D208.189 and D208.193 100% reception. Active poaching transmitters E200.125 and E200.126 100% reception, response to 20-MΩ sweep correct. Add A3028C-AA number C207.137 to poach.