So the testing thermometers we use for determining final temps, maintaining temps, and tracking our cooling process are "Guaranteed Accurate for Life" and come with the claim "there is no need of field adjusting of calibration settings and no risk of introducing error into the instrument." In fact, there does not seem to be a way to calibrate them. They are NSF, CE, WEEE, RoHS certified.
Does this mean for these instruments I only need to periodically check and record their accuracy, but don't need to maintain a calibration log?
Thoughts?