Checking the Thermometer – Probe

Thermometers must be checked at least every 12 weeks to make sure that they are providing accurate temperature readings, or whenever there is reason to think the thermometer is not working correctly. Some people check more often.

How to do the ice point check

This check must be done if the thermometer is used for checking cold foods.

  1. Half fill a glass with broken or shaved ice – you can scrape some ice from the side of a freezer.
  2. Add a small amount of water until it is visible at the bottom of the glass.
  3. Insert the thermometer into the mixture, leave until the temperature display is steady.
  4. Do not let the thermometer touch the sides or bottom of the glass.
  5. Record the result in the table below. If the result is outside the range, write down the action taken in the table.

How to do the boiling point check

To be done only if the thermometer is used for checking hot foods.*

  1. Boil unsalted water in a pot.
  2. Once boiling, insert thermometer and leave it until the temperature display is steady.
  3. Do not let the thermometer touch the sides or bottom of the pot.
  4. Record the result in the table below. If the result is outside the stated range, write down the action taken in the table.

*If you do not use the boiling point check you must use another validated method for calibrating a thermometer used for measuring hot foods.

Calibration of Infrared (IR) Thermometers

Either follow the calibration instructions that come with the thermometer or ask the business you bought it from for advice on when it should be calibrated, how this should be done, and who should do it.

  • The reading in iced water should be between –2°C to +2°C; if outside this range, the unit should be replaced or returned to the supplier to be recalibrated but this often can’t be done.
  • Infrared thermometers don’t work on shiny surfaces so it is worth laying a tissue over the ice slurry. Thanks Stephen for this idea.
  • A boiling point calibration is not practical.

Follow the link below to download your own thermometer calibration form.

Thermometer calibration