Typically a channel will read “UNDER” or “OVER” when water has entered the SIM of the Kaye Validator 2000 data logger and the cold junction has become wet. Check each thermocouple wire to ensure that you have added drip-cuts to each wire 1m from the SIM to allow the condensate to drain away from the sheathing. Sometimes a broken thermocouple is replaced with a new thermocouple but a drip-cut has not been added to the new wire and water finds it’s way into the SIM.
The SIM should be opened and allowed to dry out. Paper towels should be used to get rid of any excess water. A high pressure air source can be used to blow away excess water also. The channel should return to a room temperature value once it is fully dried out. Ensure that you have rectified the source of the water before proceeding with further studies. You may notice that the wire terminations have oxidized (looks like white powder) due to the presence of moisture. A small piece of emery paper connected to a narrow wire or flat head screwdriver can be used to restore the terminals.