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ad5933 phase measurement problem

Question asked by i2cusb on Jun 30, 2015
Latest reply on Oct 12, 2015 by i2cusb

hey sir,

          I have a doubt concerned with phase measurement of ad5933. here is my calculation parameters,

rfb=10 kohm

rcal=5.5 Mohm

frequency 30 khz,

gain=1,

voltage=2 vpk-pk

 

i calibrated the system using 5.5 Mohm and i got the phase degree=-26.56. and i replaced the calibration resistor and place a capacitor of 22 pf and i got the phase=17.73.

 

According to the data sheet the formula is phase of the system=system phase-unknown phase.

therefore -26.56-17.73=44.29.where i should get -90 degree.

Is my method of phase calculation is right???

 

HOW TO SWEEP THE FREQUENCY,        when i am setting start frequency=30khz and frequency increments=10khz and number of increments=7, where i am sweeping 30khz to 100khz, my osciloscope shows only 30khz,its not get sweeped why???

 

 

Impedance calculation is accurate using AD5933, but phase measurement is not up to the mark!! why??????

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