We had some difficulties with a AD7730.
After startup, the AD value is not consistent, once it start with 1,8 * 10^6 and the other time with 1.9 * 10^6.
In the attachment a picture of this behavior ("Different Zero Points.pdf").
We've set up this test with an automatic test-program. The microcontroller resets themself after a period of time.
These are the spikes down to zero.
The AD converter is setup with a interal full calibration and internal zero scale calibration.
The AD conversion is measured in UNIPOLAR mode with a range of 0-20mV with the DAC on +2.5mV.
It occurs with Ch0 of the AD7730, so the input with AIN1+ and AIN1-
The input filter between AIN1+ and AIN1- had recently changed.
Old type: see attachment: "Old filter.jpg"
New Type: see attachment: "New Filter.jpg"
The problem occurs with the Old type off the filter. With the new type we've seen no problems.
Does anyone recognize the described problems?