AD5933 synchronizing different frequency sweep ranges issue

Hello, everyone, I am using AD5933 with Arduino, I can measure impedance from 47ohm to 1Mohm in the frequency range(10Hz-100kHz). I have measured impedance at different frequency ranges by using different MCLK external programmable oscillator DSL1077. Now I want to measure impedance at whole frequency sweep at a time. I have implemented logarithmic frequency sweep, so for this, I am changing my start frequency register every time for performing logarithmic frequency sweep by setting increment frequency register and number of increment register as zero.
when I have applied from 10Hz-100 kHz I am not getting the accurate result I have uploaded data in terms of real and imaginary (i have measured 47-ohm resistor with 47-ohm RFB). Although the clock frequency is changing with respect to frequency sweep. if I apply each frequency sweep separately like (5kHz-100Khz) OR (10Hz-20) etc, I am getting good results. 

how can I measure whole frequency sweep accurately, do I need to measure gain factor for each sweep separately.?
my output excitation voltage is 1.98Vp-p, and the PGA gain is X1.



add output and feedback resistor value
[edited by: aitzaz at 12:53 AM (GMT 0) on 9 Jul 2019]
Parents
  • It would be useful to share some more information regarding your setup, is there an AFE? 47 Ohm RFB and 47 Ohm resistor require your system to pass p-p current of 42 mA, which is pretty high and would require some additional circuits around the AD5933 to be generated.

    How do you determine when you are getting "accurate result"? Ideally, gain and system phase should be calibrated at every frequency point within your sweep regardless of MCLK source. Using single-point or dual-point calibration described in the datasheet works only for narrow-range frequency sweeps.

Reply
  • It would be useful to share some more information regarding your setup, is there an AFE? 47 Ohm RFB and 47 Ohm resistor require your system to pass p-p current of 42 mA, which is pretty high and would require some additional circuits around the AD5933 to be generated.

    How do you determine when you are getting "accurate result"? Ideally, gain and system phase should be calibrated at every frequency point within your sweep regardless of MCLK source. Using single-point or dual-point calibration described in the datasheet works only for narrow-range frequency sweeps.

Children