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AD5934 - Problem to determine gain factor and feedback resistor

Question asked by ZE-CM on Jun 18, 2012
Latest reply on Jun 20, 2012 by LiamR

Hi,

 

Currently I am studying on piezoelectric and using AD5934 to measure the impedance of Piezo disk. However, we do not get similar value result when we compare to the commercial impedance analyser.

 

We set the frequency range from (1kHz to 10KHz) with step frequency 100 Hz. We attempt to measure the impedance in the range from 500 ohm to 20k ohm. MCLK clock input is 4MHZ. Calibration Resistor is equal to RRFB. Variable RRFB value (1k to 10k) is tested to compare with the commercial impedance analyser.

 

The gain factor is calculated through the formula from the datasheet.

 

GF = (1/Zcal)/mag


Comparing with the result from the commercial impedance analyser. We observe the frequency is accurate but the value of impedance is not matched to the commercial Impedance analyzer.

 

Please give me some advice to improve the accuracy and choose the correct value.

 

Best Regards,

 

ZE-CM

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