The thermometers are actually used for monitoring CCP and OPRP parameters. I am referring to ISO 2200 Clause 8.3 Control of monitoring and measuring. Based on my understanding, if the thermometers are just calibrated annually, there must be a need for daily in-house verification using ice-point method (based on operating condition) against a reference thermometer. These digital probe type thermometers are used daily in the processing lines and might possibly be dropped or subjected to shock that could possibly affect its calibration hence the requirement for daily verification. I want to be sure if my understanding is correct regarding this.
Brief summary my thermometer Procedure (not iso22000 but I anticipate most FS Standards are similar regarding basics) –
(1) digital thermometers are used to routinely monitor locations at temperatures of approx (a)0degC, (b) -18degC, ©100degC
(2) one master thermometer, X, exists which is externally/annually calibrated so that its errors at the above 3 temperatures, typically within +/- 0.5degC. are known.
(3) X is used to create 3 sub-master thermometers of known, acceptable, error for monitoring (a), (b), (c) using ice/water, cold-room, boiling water/steam respectively.
Verification procedure is to weekly repeat step (3). This frequency is “risk-based” via historical data.