You must challenge your metal detector system as often as possible.
You can only guarantee that your product is free of metal in the intervals when it has been tested. Anything else is suspect.
You must have some test wands, cards or similar; and challenging the detector takes only a minute or two.
I like doing it at the beginning of each shift at least, as part of the QA procedures.
Cooking? I do not understand what oyu mean?
Temperature probes must be recalibrated and that is your guarantee of achieving the right temperatures.
Edited by titrisol, 16 October 2013 - 07:58 PM.