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Voltage measurement (OCP, open circuit potential) using the AD5940 resp. ADuCM355

Thread Summary

The user seeks to measure open circuit potential (OCP) on an electrochemical sensor using the ADC5940 or ADUCM355. The final answer confirms that the front-end buffers of the ADC have high input impedance suitable for OCP measurements, and suggests connecting SE0 and RE0 directly to the ADC MUX inputs. The accompanying answers clarify that the LPTIA is not typically used for OCP measurements and provide an alternative method using the PA as a voltage follower with a common ground reference.
AI Generated Content

Hello,

we would like to use the ADC5940 respectively the ADUCM355 for voltage measurements (OCP, open circuit voltage) on an electrochemical sensor. Concerning this issue, two questions occurred. I guess ADC5940 and ADUCM355 are somehow similar.

1)We want to make a shortcut between the pins CE0 and RE0 and then measuring the voltage between CE0/RE0 and WE0 (OCP). Is it possible to measure that voltage by setting the MUXSELP-bits of the ADCCON-register to 01110 (page 70, ADuCM355 Hardware Reference Manual, https://www.analog.com/media/en/technical-documentation/user-guides/ADuCM355-Hardware-Reference-Manual-UG-1262.pdf respectivley page 61, AD5940 datasheet, https://www.analog.com/media/en/technical-documentation/data-sheets/AD5940-5941.pdf)

2) Which magnitude would be the referring input impedance?

Kind regards

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