Intraperitoneal Transmitter (A3054) Manual
| Description |
| Versions |
| Operation |
| Design |
[04-MAR-26] The Intraperitoneal Transmitter (IPT, A3054) is a pill-shaped implantable telemetry sensor designed for implantation within the peritoneal cavity of a mouse or rat. The A3054 Family of IPTs is the first family in our Second Generation of telemetry sensors, and is currently in development. 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. Its pill-shaped, silicone-coated body provides stainless steel suture loops so that it may be secured within the peritonal cavity. The IPT can be programmed at the factory to tansmit any combination of measurements from its available sensors. It can be turned on and off and re-programmed while implanted using its on-board crystal radio. Its ECoG amplifiers can be configured with AC or DC inputs, and they can be configured for any of the bandwidths 20, 40, 80, and 160 Hz. For these bandwidths, the ECoG signals will be transmitted at 64, 128, 256, and 512 SPS (samples per second) respectively. The A3054's accelerometer can be configured to provide 1 SPS of scalar activity measurement, or it can be configured to provide a one, two, or three-dimensional acceleration measurement with sample rate 32 SPS or 128 SPS per axis. The A3054's temperature sensor can be enabled to provide 1 SPS of body temperature with absolute accuracy ±0.05°C.
When you receive and IPT, it will arrive in a box with a built-in magnet. The IPT hibernates when it is near a magnet. When you remove the IPT from its box, the IPT powers up and initializes itself. During initialization, a white indicator light flashes three times and will be visible through the encapsulation at the base of the IPTs electrode leads. After the light flashes three times, there will be a pause of one second, and the light will flash zero to ten times to communicate that remaining battery capacity is between 0% and 100%. Once the IPT completes its initialization, it will execute its activation protocol. The activiation protocol tells the IPT whether it should remain idle and wait for an activation command, remain idle for a certain amount of time before activating of its own accord, to activate until it receives an deactivation commmand, or to activate for a certain amount of time before deactiviating of its own accord. When active, the IPT executes its telemetry protocol. The telemetry protocol tells the IPT which measurements to perform and how to transmit them with telemetry messages. If you have no command transmitter yourself, we will ship IPTs with the basic activation protocol and a custom telemetry protocol. The basic activation protocol activates the IPT after initialization and keeps it active indefinitely. You can deactivate it by placing it back in its box or by sending it a deactivation command, but by assumption: you don't have a command transmitter, so you cannot deactivate it with a command. The custom telemetry protocol performs measurements and transmit messages according to your specifications. If, however, you do have your own command transmitter, we will ship your IPTs with the pre-programming activation protocol and a demonstration telemetry protocol. The pre-programming activation protocol keeps the IPT idle until it receives an activation command. Following receipt of an activation command, the IPT starts executing the demonstration telemetry protocol, and will continue to do so for about ten minutes, after which the pre-programming activation protocol will deactivate the IPT, returning it to its idle state. The demonstration protocol exercises the IPT's sensors and transmits signal in such a way as to confirm the functioning of the device. With your command transmitter, you can re-configure the IPT by uploading a new activation protocol and a new telemetry protocol using the IPT Manager program built into our LWDAQ Software. The IPT will not forget its new protocols when they hibernate.
The A3054 IPT is the first of our Second Generation telemetry sensors. See the Operation section for our most current summary of the IST features and options. The electronic circuit design is complete and the schematic is drawn and scanned. Our A305401A four-section rigid-flex circuit board is layed out. We are working on a prototype rigid-only breadboard with calibration and programming connections for our first tests of the design. We expect to be working on the breadboard in April 2026. Final design will take place in May 2026. The first prototype A3054-family IPTs will be ready to ship to test sites in July 2026. See the Design page for the progress updates.
[23-FEB-26] We define the following part numbers for versions of the A3054 family of Itraperitoneal Transmitters (IPTs). The part numbers all begin with "A3054".
| Version | Battery Capacity (μA·d) |
Volume (ml) |
Mass (g) |
Operating Life (dy) |
Shelf Life (mo) |
|---|---|---|---|---|---|
| A3054X | 3500 (2×SR936SW) | 1.7 | 3.2 | 35 | 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, N is the number of active biopotential channels, and R is the total sample rate for all active biopotential channels. 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.
[04-MAR-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.
All members of the A3054 Family of IPTs hibernate when in contact with a magnet. When hibernating, we say the IPT is sleeping. While sleeping, the IPT will not respond to commands nor transmit any information. Its internal circuits are powered down. The only component on the board that is doing anything it its magnetic sensor, which is detecting the magnetic field. 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. Even the IPTs with the smallest batteries can hibernate for months and still retain 90% of their battery capacity.
As soon as we remove an A3054 IPT from its box, it wakes up and executes its initialization protocol. The initialization protocol is a fixed feature of the IPT and cannot be re-configured outside the factory. During initialization, the IPT flashes its white indicator lamp three times. After a second, it flashes the same lamp zero to ten times to indicate remaining battery capacity. After initialization, the IPT executes its activation protocol. The activiation protocol tells the IPT when and for how long to execute its telemetry protocol. The activation protocol might instruct the IPT to begin executing the telemeetry protocol immediately, and do so indefinitely. Or it might instruct the IPT to remain idle, waiting for commands. The activation protocol we can re-configure with a command transmitter and the IPT Manager tool in the LWDAQ Software. In its idle state, the IPT consumes 30 μA. A typical mouse-sized IPT with a 3500-μa·d battery capacity, can remain idle for four months before it exhausts its battery. To activate, deactivate, query, or re-program an IPT, we need a command transmitter, such as a Telemetry Control Box (TCB-B16).
When active, the A3054 IPT executes its telemetry protocol. This protocol tells the IPT which measurements to make and what signals to transmit. The telemetry protocol defines the measurements, sample rates, channel numbers, and bandwiths. Each IPT has a factory-assigned four-digit hexadecimal code that cannot be altered once the IPT has left our factory. 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. We can upload a new telemetry protocol to any IPT at any time with our command transmitter using the IPT Manager tool of the LWDAQ Software.
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, but it does provide an estimate of remaining battery capacity. Instead, the IPT keeps track of how much of its capacity it has used. It periodically increments a charge consumption counter in its non-volatile memory. Even if we put the IPT to sleep, this counter is retained. We can request a battery capacity measurement with the IPT Manager and the IPT will deliver 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.
[04-FEB-26] For details of the design, development, and production of the A3054, see its Design page.