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AD7190 - Channel interaction

Question asked by ElectronAby on Aug 6, 2012
Latest reply on Aug 9, 2012 by MaryMc

Hi,

 

I am using 3 channels of the AD7190. They are being used in Unipolar mode with Chopper enabled and with gain of 1. My reference is 2.5V and my circuit is built around the AD7190 evaluation board.

 

I am acquiring data in continuous read mode and normally everything is fine.

 

I am reading inputs from three sensors.

 

1) CH6 = S type thermocouple 0-10mV amplified using instrum amp to give about 0-2300mV input range to ADC. Negative of thermocouple is AGND.

2) CH5 = Thermistor circuit giving about 0.5 to 2V input range to ADC.

3) CH7 = Zirconia oxygen sensor giving about 0-1200mV input range to ADC. Negative of sensor is AGND.

 

My issue is that when CH7 input is connected to the sensor the other channels seem to rail (sometimes randomly)

 

Any ideas would be appreciated.

 

Tahnkyou.

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