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AD5933 analyzing 0.5 Hz and 0.1 Hz

Question asked by Lunatic91 on Jun 22, 2015
Latest reply on Feb 17, 2016 by musach
Branched to a new discussion

Hello all,


I'm using the AD5933 to analyze a complex impedance across the frequency range of 100kHz - 0.1Hz, collecting data at two points per decade. I do mini-sweeps at each point to achieve results with minimal error. I've accomplished the setup and functionality of the system and can achieve good results from 100kHz all the way down to 1 Hz. I've tried almost everything I could possibly think of and then some to get any reasonable data out of the device at 0.5 and 0.1 Hz, but nothing is working.


Consistently, for 0.5 Hz, I'm reading an Impedance magnitude back of an extremely small decimal number between one and zero (or sometimes NaN results). For 0.1 Hz, I am consistiently reading back the exact value for my calibration impedance that I hard-coded into my micro-controller's firmware. I know this usually means the device read the same impedance for both calculating the gain factor and the test impedance, but I've verified numerous times that this isn't the case. I have also verified with my oscilloscope that the device is outputting the wave at the right amplitude and frequency.


So I guess my first question is that, the datasheet says the device has a resolution of < 0.1Hz, which I would imagine means it can read all the way down to 0.1 Hz? And if it can, could someone point me in the right direction to try and solve my problem?


Thanks a lot for the help,