i designed AD5933+AFE circuit by referring evolution board and interfaced with atmega16 micro controller. i getting problems with calibration and measurement. my problems are
1.i'm getting different real and imaginary values whenever i power off and power on the board.
2.After calibration using Rfb =150k with Rcal =150k i'm getting around 150k impedances for 150k,200k and 300k unknown impedances.why its happening i refer my code with previous discussions and it is correct.
i have some doubts
1. is delays changes the operation of the impedance's.
2. internal frequency will give correct impedance output?
3. i used 1MHz ext crystal to MCLK. for 1mhz crystal how much frequency we can give
4. whether this part work for 3.3v
i'm attaching schematic plz suggest any changes required
plz clarify i'm totally confused i referring every discussion in analog devices nothing help me.