We are attempting to read temperature values using type K thermocouples and the DT800 is returning 99999.9 for every temperature value. By searching forum messages we discovered this indicates an error condition.

The value we should be reading should be between (approx) 20 to 160 degrees F. We attached a meter to the wiring at the end where we plug into the DT800 and we see accurate values so this leads us to think it is not a wiring issue.

In total we are attempting to read 13 different temperature values from the same number of thermocouples. The fact that every single channel returns an error condition value leads us to think it's a configuration issue of some nature.

We are using two different DT800s. We have used one of these units in the past on an almost identical setup (reading temperatures from type K thermocouples) and it operated correctly. The other DT800 is a new unit. Each DT800 is attached to a separate notebook computer.

Any help would be greatly appreciated.

Good afternoon thilgesc,

It sound like you are suffering from a ground loop.
If the thermocouples are bare tipped and in contact with a conductive surface or medium then the thermocouples can pick up stray voltages.

It is also possible for different thermocouples to be picking up different voltages for different areas being monitored. This can lead to the common mode range being exceeded.

Have you tried either electrically isolating the thermocouples from the surface being measured or grounding the DT800 to the item being monitored?

Cheers,
Roger