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AD5934 measurement problem

Question asked by wxtyz on Feb 13, 2017
Latest reply on Feb 15, 2017 by Snorlax

Hi,

 

I have the EVAL-AD5933EBZ to which I have hooked a AD5934 on SCL and SDA pins to try to get data from a different chip.

For test purposes I have tried the following:

- Vpp = 2V, want to measure without external AFE.

- set to external clock, tied 16MHz to MCLK;

- RFB = 24kohm;

- RCAL = 25kohm;

- Zunknown -> a 220pF capacitor for measuring at 10kHz;

Therefore, expecting to measure around 72kohm, I get ~49kohm. If I change to a AD5933, that one seems to measure correctly.

 

I'm a newbie and don't know much, but is this expected to happen? I thought that if I adjust the values for registers f_start, f_incr, then I can expect to get roughly the same Z value. Can anyone give me any advice?

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