Calibrating thermometers
All facilities are required to have at least one probe thermometer accurate to +/-1°C, available for use at all times. Your thermometer does not have to be expensive, but must meet the minimum requirements.
To ensure your thermometer meets the required accuracy, you will have to calibrate it regularly. It is recommended that this is done around once every six (6) months. This frequency may vary depending on the use of the thermometer.
If you are calibrating your thermometer yourself, it is important to use both the ice point and boiling point methods to ensure the thermometer is accurate in its upper and lower ranges.
Ice point calibration
To calibrate your thermometer using the ice point calibration method, follow these steps:
- Fill a plastic container with crushed ice
- Mix enough chilled water to produce slurry, but not enough to float the ice
- Stir the slurry vigorously, insert the probe of the thermometer into the iced slurry
- Wait for at least three minutes and then record the reading
- To ensure the readings are correct and accurate, take readings at least two minutes apart and the results should be within 1°C of each other. The reading should be 0°C (if the readings do not agree then you should have the thermometer replaced or serviced)
- Record your readings.
Boiling point calibration
To calibrate your thermometer using the boiling point calibration method follow these steps:
- Heat a saucepan of water on the stove
- Wait for the water to come to a continuous rolling boil
- Insert the probe of the thermometer into the water
- Wait for at least three minutes and then record the reading
- To ensure the readings are correct and accurate, take readings at least two minutes apart and the results, should be within 1°C of each other. The reading should be 100°C (if the readings do not agree then you should have the thermometer replaced or serviced)
- Record your readings.
Mechanical calibration
Some more expensive thermometers come with a mechanical calibration unit. Follow the manufacturer’s directions on calibrating your thermometer this way. Alternatively, you may be able to return your thermometer to the manufacturer for calibration.
Records
Keep the following records when you calibrate your thermometer: