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PGA309: Sensor compensation without temperature measurement.

Alistair Newcombe
Prodigy 60 points

Part Number: PGA309

I'm looking into the use of a PGA309 chip for active compensation of a medical pressure sensor. For this application we want to be able to calibrate the sensor outside of the patient, for both temperature and pressure, before implantation.

As I am aware PGA309 does temperature compensation through changing the value of the Zero DAC by using a lookup table. In order for this to be accurate in our application it would require a temperature probe to be placed at the same point as the pressure sensor in the body, this is not desirable. Using the internal temperature sensor would give us inaccurate measurements as the internal body temperature and room temperature will be wildly different. 

If an external temperature sensor is not connected to the PGA309 will the internal temperature sensor be automatically used? Or is there a way to disable the temperature compensation through the lookup table so that the value of the Zero DAC will not change with external temperature fluctuation. We want to be able to passively compensate for the usable temperature and pressure range, not continually compensate for changes in temperature. Would the PGA309 be able to achieve this? 

Thanks.

  • 0
    TI__Mastermind 19710 points
    Hi Alistair,
    Temperature compensation can be configured to use the PGA309 temperature sensor, or an external sensor if desired. If you don't need the linearization functionality, it should be possible to just write your room-temperature calibration to the first entry in the lookup table, then set the second temperature to 0xFFFF, which signals the end of the lookup table. This should cause the PGA309 to use only the first entry in the lookup table.

    It may also be possible to use the bridge itself as a temperature sensor (if desired) by adding either a top-side or bottom-side series resistor at the PGA309. For more detail on this, see section 2.7.2 (starts on page 43) of the PGA309 user's guide.