Intraperitoneal Transmitter (A3054) Manual
| Description |
| Versions |
| Operation |
| Design |
[11-FEB-26] The Intraperitoneal Transmitter (IPT, A3054) is an implantable telemetry sensor currently under development at Open Source Instruments Inc. The IPT provides three ECoG/LFP/EEG inputs with shared reference potential, a single EMG/ECG input with its own reference potential, an accelerometer, and a thermometer. It is pill-shaped and provides stainless steel suture loops so that it may be secured within the intraperitonal cavity. The IPT can be programmed at the factory to enable and tansmit any combination measurements form its available sensors, or it can be re-programmed while implanted using its on-board crystal radio. Its ECoG inputs can be configured for AC or DC coupling, and for bandwidth 20, 40, 80, or 160 Hz at 64, 128, 256, and 512 SPS (samples per second) respectively. Its accelerometer can be disabled, or enabled to provide a 1 SPS scalar activity measurement, or configured to provide a three-dimensional acceleration measurement at 32 SPS or at 128 SPS. Its temperature sensor can be disabled or enable to provide 1 SPS of body temperature with absolute accuracy ±0.05°C.
We configure each IPT through its on-board crystal radio. We can do this at our factory, so as to provide you with IPTs in a configuration you choose at the time of purchase. When you receive the IPT, it will be arrive in a box with a magnet inside, hibernating in the presence of the magnetic field. When you remove the IPT from its box, it powers up and immediately starts transmitting signals according to your specification. Another way to configure an IPT is to equip yourself with one of our command transmitters, such as the TCB-B16 or A3029C. Now you can re-program the IPT yourself, using the IPT Manger Tool in our LWDAQ Software. You can re-program the IPT while it is implanted, or you can disable the IPT while it is implanted, in order to conserve its battery life. You can re-program, store in the IPT's magnetic box, and transport to your animal facility for implantation. When you remove the IPT from its box, it will wake up from hibernation and begin executing your measurement program.
We expect the first prototypes to be available in June 2026. We are developing the functionality of the A3054 now, and laying out the first version of the printed circuit board. See the Operation section for our most current summary of the IST features and options.
[03-DEC-25] We define the following part numbers for versions of the A3051 blood pressure monitor. The part numbers all begin with "A3051", after which there is a letter code identifying the battery type, an integer code that specifies the pressure sample rate, followed by one or more modifier letters. An "H" is for high-pressure range. A "T" indicates the addition of a 64 SPS temperature measurement.
| Version | Battery Capacity (μA·d) |
Volume (ml) |
Mass (g) |
Operating Life (dy) |
Shelf Life (mo) |
|---|---|---|---|---|---|
| A3054X | 3500 (2×SR936SW) | 1.7 | 3.2 | 24 | 12 |
The shelf life is the time it takes to use up 10% of the battery capacity when the device is left inactive on the shelf. The operating life is how long the device can produce reliable measurements when starting with a fresh battery. We calculate the operting life using the following formula for operating current.
Where I_a is the active current and R is the total sample rate for all biopotential channels combined. Here we are assuming a 1 SPS temperature and activity measurement. We can configure the IPT for faster monitoring of acceleration, in which case we must add the current consumed by the accelerometer measurements, which is not included in the above formula.
[11-FEB-26] In the paragraphs below, we describe how we expect the IPT to perform when it is ready to ship. We will be re-writing these paragraphs as we go through development, adding features that turn out to be easy to add, and removing features that turn out to be impractical. The paragraphs are written in the present tense, implying that the features and software exist already, but this is not the case. These paragraphse are intended to be the Operation chapter when the device is released.
The A3054 IPT hibernates when in contact with a magnet. We say it is sleeping. While sleeping, the IPT will not respond to any commands nor transmit any information. We store IPTs in little boxes with built-in magnets so that they hibernate on the shelf. While asleep, the IPT consumes less than 1 μA from its battery, so that even the IPTs with the smallest batteries can hibernate for months and still retain 90% of their battery capacity. As soon as we remove the IPT from its box, it wakes up. What an IPT does when it wakes up depends upon how it has been configured. In the default configuration the IPT wakes up in its dormant state. In the dormant state, the IPT listens for radio-frequency commands, but otherwise takes no measurements and makes not transmissions. In the dormant state state, the IPT consumes 20 μA from its battery. A typical mouse-sized IPT with a 3500-μa·d battery capacity, can remain dormant for eighteen days and still have 90% of its battery capacity left.
An IPT in its dormant state must be configured with one of our telemetry command transmitters, such as a Telemetry Control Box (TCB-B16). Each IPT has assigned to it a four-digit hexadecimal code. When we transmit commands, we use this code to identify a particular IPT. All IPTs within range of the command transmitter will parse and examine every command, but only the IPT with the specified ID will respond. There is, however, a wildcard ID, 0xFFFF, to which all IPTs respond. Configuration and monitoring of IPTs in our LWDAQ software is provided a dedicated IPT Manager Tool. Once configured to perform measurement and transmission, the IPT will remember its configuration even if we send it into hiber nation with a magnet. The configuration saved in its non-volatile memory is its active configuration. At any time, we can use a radio-frequency command to move the IPT from its active state to its dormant state, or from the dormant state to the active state. Furthermore, we can configure the IPT so that it wakes up and enters its active state instead of waking up and entering its dormant state. If you have a telemetry system that lacks command transmitters, you will still be able to use the IPT. We will be able to configure the IPT here at our factory to your specifications, and then ship them hibernating so that when you wake them up, they turn on in the state you requested. But for those of you who do have command transmitters, you can re-configure your IPTs while they are implanted, prior to implantation, or well in advance before placing them back on the shelf to hibernate.
The A3054 IPT provides three ECoG inputs with a shared reference potential. These are designed to record ECoG, LFP, or EEG. They can be used with depth electrodes or surface electrodes. The amplifiers run off a 1.80-V power supply and use 0.90 V as their ground potential. The ECoG shared reference potential is equal to the amplifier ground potential, and is therefore 0.90 V above the potential of the negative battery terminal. We can configure each of the ECoG amplifiers individually with DC coupling or AC coupling. When configured with DC coupling, the amplifiers respond all the way down to 0.0 Hz, so they can detect spreading depolorizations. The amplifier gain with DC coupling will be set to ×10, giving the amplifier input a ±90-mV dynamic range, which is adequate to accommodate the galvanic potentials generated by metal electrodes. When configured with AC coupling, the amplifiers will introduce a high-pass filter with corner frequency 0.3 Hz. The amplifier gain with AC coupling will be ×45, giving the amplifier a ±20-mV dynamic range.
The three ECoG amplifiers contain a low-pass filter with 320-Hz corner frequency. We can enable sampleing of each ECoG input separately. If we enable an input, the IPT will sample the amplifier output at 1024 SPS. We can configure the IPT to transmit 64, 128, 256, or 512 SPS for each channel. If it transmits 64 SPS, it takes the average of 16 samples and transmits this average value sixty-four times per second. If it transmits 512 SPS, it transmits the average of 2 samples. The bandwidth for the four available sample rates is 20, 40, 80, and 160 Hz. Each ECoG telemetry signal will be assigned its own telemetry channel number by configuration. The channel numbers need not be consecutive. Telemetry channel numbers lie in the range 1-254, subject to the restriction that their remainder after dividing by sixteen cannot be zero or fifteen. Thus 31 and 32 are not legal channel numbers, but 33 and 46 are.
The input impedance of the three ECoG inputs is 1.0 MΩ. At any time, the IPT can, in response to a command, measure the impedance of its ECoG electrodes in the following manner. The IPT configures all ECoG inputs for DC coupling. It applies a −1 mV step to the ECoG shared reference potential. From the amplitude of the step we see in each ECoG input, we can deduce the resistance between the reference electrode and each ECoG electrode with a precision of roughly 0.1% of the ECoG amplifier input impedance, or 1 kΩ.
The single EMG input has its own reference potential. Its bandwidth is 2-320 Hz and its input dynamic range is ±20 mV. When enabled, we sample this input at 1024 SPS and take sample averages to produce a transmitted sample rate of 64, 128, 256, 512 or 1024 SPS. During configuration, we assign a telemetry channel number to the EMG input.
The accelerometer can be configured in one of four ways. It can be disabled, it can provide 1 SPS activity measurement, or it can provide continuous acceleration measurements at two sample rates. The activity measurement is an eight-bit value derived from the sum of squares of the individual x, y, and z acceleration components. We divide this sum of squares and limit it so as to produce a value 0-255. When this value is less than 4, the animal is not moving at all, not even breathing. When the value is less than 32, the animal is resting. When it is between 32 and 127, the animal is moving around. When 128 or greater, the animal is scratching vigorously, jumpring around, or convulsing. The IPT transmits this eight-bit value as an auxiliary telemetry message. All auxiliary messages transmitted by the IPT will be displayed by the IPT Manager. We can also configure the accelerometer to provide 32 or 128 SPS of x, y, and z acceleration, in which case we assign the x, y, and z signals their own telemetry channel numbers and the accelerations are transmitted as unsigned, sixteen-bit integers for which 32768 is the zero value.
The temperature sensor can be turned on or off. If on, it provides a 1 SPS eight-bit temperature measurement with absolute accuracy ±0.05°C and resolution 0.03125°C/cnt. This measurement is zero at a temperature we transmit to the IPT during configuration. If we transmit 37°C as the zero-point, the temperature will span the range 33.0000°C to 40.96875°C for values 0 to 255. The eight-bit value will be transmitted with an auxiliary messages. These messages will be captured, combined, and displayed by the IPT Manager.
The IPT provides no measurement of battery voltage, because the voltage on its silver-oxide batteries does not tell us much about the remaining capacity in the battery. Instead, the IPT keeps track of how much of its capacity it has used, but adding to a consumption counter in its non-volatile memory. Even if we put the IPT to sleep, this counter is retained. We request a battery capacity measurement with the IPT Manager and the IPT delivers the measurement in an auxiliary message, which the IPT Manager will display. The response is an eight-bit value that is 0 when the battery is fresh and 100 when it should be exhausted.
When we configure an IPT, it remains awake and inactive until we activate the configuration by sending it an activate instruction. Once active, the IPT starts transmitting as its configuration has requested. We can deactivate the IPT at any time without erasing the configuration. We can instruct the IPT to run for two hours and deactivate itself if we like, or we can provide it with a schedule of activation so that it turns itself on for an hour every day, or ten minutes every hour.
[04-FEB-26] For details of the design, development, and production of the A3054, see its Design page.
