It is only necessary to calibrate a thermometer over the range in which it is going to be used over.
For example—a thermometer used to measure the temperature of food stored in a chiller should be calibrated over the range that the food is required to be within. The temperature may need to be
5 °C or less and above
0 °C so it doesn’t freeze.
In this case, calibration points of
0 °C & 5 °C would be appropriate.
You may also be using the thermometer to check that frozen product is below
-18 °C and so adding a calibration point of
-20 °C would suit.
If you are also using the thermometer for confirming that cooked food has reached the required temperature, you may add say
60 °C and
82 °C as calibration points.
