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I've designed a circuit around the TI LMP91000, a configurable Analog Front End (amperometric potentiostat, for use with electro-chemical gas sensors). In addition the circuit includes a 2.5V reference (for VREF on the LMP91000), and an 18-bit ADC.

Once the sensor is installed in circuit, it's very difficult to remove it without doing harm. I've experienced a significant number of failures late in the testing process (e.g. during calibration), that I don't understand the root cause of yet, but which I suspect are related to undetected manufacturing defects in the underlying circuit (i.e. not a problem with the sensors themselves). The upstream testing that I do right now is limited to just establishing I2C communication with the LMP91000 and the ADC before installing the sensor. If I could identify problems earlier, I could potentially fix them before installing sensors.

Is there a way to temporarily attach an external circuit in place of the electro-chemical sensor (i.e. using pogo pins connected to the working, counter, and reference electrode inputs) to inspire the LMP91000 to output an expected voltage so that I can demonstrate the analog front end is working correctly before installing a sensor? What would the composition of such a circuit need to be?

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  • \$\begingroup\$ Do you do any testing on the circuit prior to installing the sensor? What is the symptom? What is your circuit? Are you 100% sure the sensors are not damaged? \$\endgroup\$ – Andy aka May 29 '15 at 8:28
  • \$\begingroup\$ @Andyaka regardless of whether the sensors are damaged, I'd like to be able to test the driver boards independently. I'll post a schematic shortly. \$\endgroup\$ – vicatcu May 29 '15 at 17:01
  • \$\begingroup\$ The circuit - where is the LMP91000? What is the ADC and which is the 2.5v reference? \$\endgroup\$ – Andy aka May 29 '15 at 17:16
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I'd suggest looking at the sensor output characteristics and coming up with a circuit that will mimic the output, and use Pogo pins to connect this test circuit up to your main board. Once you can excite your circuit with known good signals, you have a chance to troubleshoot it. Until then, it sounds like you're flying blind.

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