When setting up a datalogger always ensure that you select the HOLD boxes on the temperature range, and set a delay of at least an hour before the first reading.
Selecting the ‘HOLD’ setting means that the datalogger will continue to flash red after reading temperatures outside the set range.
If HOLD isn’t selected, then once the temperature returns to within the set range, the datalogger will flash green again, meaning that the temperature excursion won’t be noticed until the temperatures are downloaded.
Delaying the first reading for at least an hour allows the datalogger to be returned to the fridge/chiller and cool before recording. If the delay isn’t added then the first reading is room temp (or your hand) and the datalogger is already out of tolerance before it is put into the fridge.
The Practice Standard (January 2014)