SUSA Electrochemical Sensor Reference Circuit
The circuit shown on the right is SUSA's recommended reference circuit for electrochemical sensors, which is suitable for SUSA's full range of electrochemical sensors, and customers can adjust the bias control switch by themselves according to the specific model.
When you use O2 sensor, VS-VR = -600mV+/-20mV, the op-amp supply voltage is more than 2.0V higher than VS. The Vo signal goes down when the oxygen concentration increases.
When you use CO, SO2, H2S, PH3, HCN sensor, VS=VR>=0.4V. When the gas concentration increases, Vo signal goes up.
When you use NO2, Cl2, ClO2 sensor, VS=VR, VR is at least 0.4V lower than the supply voltage of op-amp. When the gas concentration increases, Vo signal goes down.
When you use NH3, NO, ETO sensor, VS-VR=+300mV+/-10mV, VR>=0.4V. When gas concentration increases, Vo signal goes up.
VR and VS need to be provided by voltage reference chip dividing voltage. At the output Vo, a level of RC filtering is added, and the RC constant is adjusted according to the need. Then add another level of amplification or follow, and then into the ADC can be.
C0 and C3 need to be adjusted according to the characteristics of your own amplifier.