Thermometer Calibration

Thermometer calibration is the process of checking a temperature-measuring device against a known reference to determine whether its readings are accurate. In foodservice, accurate thermometers are essential for receiving, cooking, cooling, reheating and holding checks. Calibration should follow the manufacturer’s instructions and the food-safety plan.

Common calibration checks

• Ice-point method: place the probe in a properly prepared slurry of crushed ice and clean water, without touching the sides or bottom of the container. A correctly functioning thermometer should read approximately 0°C (32°F).
• Boiling-point method: place the probe in vigorously boiling water without touching the pot. The expected reading is approximately 100°C (212°F) at sea level, but the boiling point decreases with altitude and varies with atmospheric pressure.

Calibration versus accuracy verification

Some thermometers allow the user to adjust the reading; others can only be checked. If the instrument is outside the permitted tolerance, adjust it according to the manufacturer’s instructions or remove it from service and replace or repair it. Record the result and action taken.

When to check a thermometer

Check thermometers at the frequency set by the food-safety plan, after dropping or damaging the device, when readings appear inconsistent and before important monitoring tasks. Use an appropriate reference method for the thermometer type and measurement range.

Example: a kitchen checks a probe thermometer using an ice-point slurry before service and records the result. If it is outside the allowed tolerance, the thermometer is adjusted or replaced before use.

Chef’s safety note: calibration does not replace correct probe placement, cleaning and sanitising between measurements, or allowing the reading to stabilise. Follow the manufacturer’s instructions and local food-safety requirements.