Sorry, I was out of office for while. I am back now. I measured the temperature of the chip and it runs around 36 to 38 degrees C. The current chip I am testing fails once every 2 minutes. It is very noisy. I used a small heat gun to warm the part up to 70 degrees C. When I did, it failed every 5 seconds. I cooled it down with freeze spray and it stopped failing. The temperature was 32 degrees C after the freeze spray. When it finally got back to the 36 to 38 degree C range, it stopped failing. Though it was still noisy, it wasn't noisy enough to fail. I then reapplied the heat till the temperature was 40 to 45 degrees C and the readings started to fail again. When it cooled below 40C, it would stop failing. Our circuit is looking for a ground fault. It works very slowly. We have two calibration cycles and two read cycles. The system test is as below: 1. Configure the circuit to measure the return line. 2. Wait 250 ms. 3. take one sample of the power supply return line. 4. wait 5ms 5. Configure the circuit to measure the power supply voltage (26vdc through a divider = 4.0vdc). 6. Wait 250ms. 7. take one sample of the power supply. 8. wait 5ms 9. configure for a high side ground fault test (should be 0vdc with no ground fault). 10. wait 1 second. 11. take a sample of the voltage (should be 0vdc). 12. wait 5ms 13. configure circuit for a low side ground fault test (should be 0vdc with no ground fault). 14. wait 1 second. 15. take a sample of the voltage (should be 0vdc). 16. wait 5ms. 17. Goto step 1. This repeats over and over.
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