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LMP91000 sensor interface

Vic McCarn
Prodigy 20 points

Other Parts Discussed in Thread: LMP91000

I have a chemical gas sensor and I need to build an electronic interface for it.  I have the LMP91000 eval board.  At one time I thought I'd need a simple potentiostat, which the LMP91000 would work well for.  However, as I have progressed I've found the best way to operate the sensor is as a resistive device whose resistance changes with exposure to the gas.  I've been using a precision digital multimeter to do 4 wire ohmic measurements thus far.  Basically the DMM puts a fixed current through the sensor and monitors its voltage to determine overall resistance.  Can the LMP91000 be set up to output a constant current (like 0.1 or 1mA) and measure the resulting voltage?

  • 0
    TI__Prodigy 725 points

    Vic,

    the LMP91000 is designed to work with "chemical cells". These needs a potentiostat to work properly. I guess the sensor you are looking into is a Metal Oxide Sensor?

    Maybe I can help you, if you tell me which gas you want to measure and which sensor you are evaluating.

    Andreas

  • 0 in reply to Andreas Kraemer
    Prodigy 20 points

    My sensor is more of a solid state type that responds to airborne chemicals such as ammonia.  It is best used with a constant current supplied to it, and then I can measure the voltage.  This 4-wire resistance measurement has proven to work well using a piece of lab equipment to provide the current and measure the voltage.  I now need to design a small circuit to do this.  I wanted to know if the LMP91000 can do this, or will I need to use separate ICs to supply current and measure the voltage.

  • 0 in reply to Vic McCarn
    TI__Prodigy 725 points

    Hi Vic,

    the LMP91000 will not work with such sensors. As you menitoned Ammonia, there are chemical cells for Ammonia, i.e. NH3 3E 100 from City Technology.

    Also, if youplan to use the Metal Oxid Sensor, we may have a part in plans, which supports such. Maybe you can just send me an e-mail to andreas.kraemer@ti.com and we could then take this disussion offline.

    Andreas