I am currently conducting testing of an AD7441R. My test consists of using only Channel A, in Current Input, Loop Powered Mode. I have enabled short circuit protection. For my testing I am using a Fluke process meter to simulate the sensor. The Fluke meter is slowly ramping the current from 4.00 mA to 20 mA and back down again. My firmware performs a single conversion every 10 minutes.
Normally the AD74412R properly measures the current as it changes. I am also monitoring the Alert Status register and have observed that I am often receiving a VI_ERR_A error.
Here is a portion of my event log:
2000-01-01 08:30:31 -> AI00:17.612
2000-01-01 08:40:31 -> AI00:15.663
2000-01-01 08:50:31 -> AI00:9.898
2000-01-01 09:00:31 -> AI00:4.795
2000-01-01 09:10:31 -> AI00:10.697
2000-01-01 09:18:29 -> AD74412R Status Change. anAPI_Ref = 1, Notification = 17
2000-01-01 09:20:31 -> AD74412R Status Change. anAPI_Ref = 1, Notification = 17
2000-01-01 09:20:31 -> AI00:5.418
2000-01-01 09:30:31 -> AI00:11.396
2000-01-01 09:40:31 -> AI00:18.032
2000-01-01 09:48:15 -> AD74412R Status Change. anAPI_Ref = 1, Notification = 17
2000-01-01 09:50:31 -> AD74412R Status Change. anAPI_Ref = 1, Notification = 17
2000-01-01 09:50:31 -> AI00:4.646
Note that before the first status change message, the current was changing every 10 minutes (at 8:30, 8:40, 8:50, 9:00, and 9:10). The next conversion should occur at 9:20 and it did, but at 9:18 and at 9:20 I received notification of two errors. Those messages indicate that the VI_ERR_A bit was set in the Alert Status Register. The errors then cease for several minutes only to return again at 9:48.This happens over and over again during the test.
It could be happening because of a problem in the Fluke meter. Or maybe it is happening because of some other reason. Do you have any thoughts or recommendations?
I think I will remove the fluke meter and install a suitable resistor in its place. This will cause a fixed current to flow. If the error then continues, it would point to a firmware / hardware problem. If it does not reoccur it would point to a problem in the Fluke meter.
Please let know your thoughts today. I hope your response can help me determine testing I can perform over the weekend.
Thanks for everything,