I had a DT800 running on test for 24hrs measuring two low voltage inputs of approx 2V. The logger was reading the channels at 10Hz. After 23hrs the logger stopped reading the voltage and simply returned readings such as 0.034.

There was no sign of a voltage spike when the readings were downloaded, suggesting it wasn't damaged by too higher voltage. It now measures bridges, thermocouples correctly but not voltage or 2 wire resistance, I have not tried any other sensors. When issued the TEST command it comes back with PASS.

Any ideas before I ship it back for repair, it is 4 years old with minimal use.

Thanks Matt

Good morning Matt,

The fact that it is measuring bridges and thermocouples correctly tell us the DT800 is reading voltages correctly.

The fact that is was working correctly for the first part of the test and is not now means that something in the system has changed and what we need to do is find out exactly what has changed.

Some diagnostics you can try;

Run the TEST command on the dataTaker without any inputs connected, If it fails then there is something wrong with the logger.

If it passes then:

1. Check for a dead channel.
   Move the voltage inputs to another channel. For example if you are reading voltages on ch1&2 then move them to the other end of the logger. If they work on the new channels that chances are the MUX chips have been damaged.

2. Check for ground loops.
   It might be a ground loop problem. Have you connected the ground side of your inputs to the AC terminal on the DT800?

Cheers,
Roger