Currently I am studying on piezoelectric and using AD5934 to measure the impedance of Piezo disk.
We have create a simple circuit for AD5934 to measure the impedance of Piezo disk and is working. However, we compare 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.
Therefore, we edit the schematic to incorporate a simple buffer by using AD8606 (same schematic in CN0217, Vcc is 3.3V) for improving its accuracy.
After we add in AD8606 in our schematic, the value of impedance is incorrect and impedance data is in a mess.
AD5934 is working fine when it work in alone. The problem should be in AD8606.
Do the feedback resistor need to be changed if a buffer is added?
Please give me some advice to debug our schematic?