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AD5933 invalid and inaccurate measures

Question asked by BerlinAnalog on Oct 24, 2017
Latest reply on Feb 15, 2018 by Snorlax

I´m using Ad5933 with AFE (AN -1252). the external clock signal is provided by DS1077. I wanna do sweeps from 10 Hz to 1 kHz. I divided my output-signal (excitation) into many pieces to perform sweeps. For example on sweep is from 10 Hz to 30 Hz with an increment size of 1 Hz and id like to perform 20 increments. I programmed a loop with 4 repeats for each frequency and I'm using the first 2 values to calculate system phase and gain factor. the last two values for measuring impedance and phase. I calculated mclk with the following formula:

MCLK = OutFreq * 16 * 1024 / NbPeriods

Number of settling cycles is 5

I get many inaccurate measures or hundreds of invalid values. decreasing settling cycles gives me more invalid values and more inaccurate measures... what could I do wrong?

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