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AD5940 used for Electrochemical Sensor - Zero not as expected

Category: Software
Product Number: AD5940/41
Software Version: ??

Electrochemical Sensor setup  - When I remove the sensor from the circuit, I would expect to see a value corresponding to my Vzero with respect to common.  I'm seeing a value very close to common.

I'm unsure of what settings I need to change in order to fix this, or if this is an expected result.


pAMPCfg->AmpODR = 0.01; /* Time between samples in seconds */

pAMPCfg->FifoThresh = 100; /* Number of measurements before alerting host microcontroller */

pAMPCfg->SensorBias = -300; /* Sensor bias voltage between reference and sense electrodes*/

pAMPCfg->LptiaRtiaSel = LPTIARTIA_24K;


pAMPCfg->Vzero = 1100; /* Vzero voltage. Voltage on Sense electrode. Unit is mV*/

pAMPCfg->ADCRefVolt = 1.82; /* Measure voltage on Vref_1V8 pin */

#define REG_AFE_LPDACSW0 0x00002124 /* AFE LPDAC0 Switch Control */

#define REG_AFE_LPDACCON0 0x00002128 /* AFE LPDAC Control Bits */

#define REG_AFE_LPDACDAT1 0x0000212C /* AFE Low Power DAC1 data register */

#define REG_AFE_LPDACSW1 0x00002130 /* AFE Control register for switches to LPDAC1 */

#define REG_AFE_LPDACCON1 0x00002134 /* AFE ULP_DACCON1 */

I'm very unsure about all of this, so any guidance is GREATLY appreciated.