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AD7190 Eval - Different Resolution found in Bipolar and Unipolar Mode

Question asked by Tandi on Mar 5, 2013
Latest reply on Mar 6, 2013 by Tandi

Hello,

 

I have used the AD7190 EVAL board to measure the battery voltage (1.5V), and the battery+ is connected to AIN+ and battery- is connected to AIN- terminals. Please see attachment for details.

 

I am also using the REF2 that comes with the EVAL board, with the following setting:

Gain = 1

Buffer = OFF

Chopping = OFF

Input: AIN1 and AIN2

FS Bits = 48 (100Hz)

SINC4

Continuous operations

Ref: 2.5V

Internal Clock

 

Running the program using Bipolar mode gives me the P-P resolution of 20.2 bits. However, once I changed to Unipolar mode, the resulting P-P resolution becomes 19.2 bits.

 

Is this expected or is there anything wrong with the input connection/software setting?

 

Thanks for your help.

 

Tandi.

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