food safety temperature
Thermometer Calibration
Check a thermometer against a known temperature and adjust it if it is off.
13 steps7 criticalLimit 3 minAlways tested
Steps
- 1Calibrate food thermometers as the manufacturer recommends, and also after an extreme temperature change, after a drop, or whenever accuracy is in doubt
- 2Ice-point method: fill an insulated container, such as a foam cup, with crushed ice made from potable water
- 3Critical stepAdd cold water so there are no air pockets
- 4Critical stepWait about 4 to 5 minutes for the mixture to reach 32 degrees F (0 degrees C)
- 5Critical stepPut the stem in the center of the cup, away from the bottom and sides, with the probe at least 2 inches into the ice water
- 6Critical stepHold it until the reading stabilizes (the needle stops moving), then record the temperature
- 7Critical stepCompare the reading with 32 degrees F (0 degrees C); the Food Code requires food thermometers scaled in Fahrenheit only to be accurate to within 2 degrees F, and those scaled in Celsius or both to within 1 degree C
- 8Critical stepIf the reading is not 32 degrees F (0 degrees C), hold the calibration nut under the dial with pliers or a wrench and adjust the thermometer until it reads 32 degrees F
- 9Repeat the procedure to verify the result
- 10Digital thermometer: verify it with the same ice-point steps; adjust it as the manufacturer instructs, and if it is inaccurate and cannot be adjusted, stop using it and send it back to the manufacturer
- 11Boiling-point method (alternative, per the county guide): put the sensor in boiling water, wait until the needle stops, and adjust a dial thermometer until it reads 212 degrees F; ask your health department or manufacturer how to handle elevation
- 12If your facility or health district uses a thermometer calibration log, record the calibration temperature and any corrective action on it
- 13Clean and sanitize the thermometer before and after each use
What graders are watching for
Tips
- Food Code 4-502.11(B): food temperature measuring devices must be calibrated per the manufacturer's specifications as necessary to ensure accuracy
- A dial stem thermometer has a dimple on the stem; insert it past the dimple, and use a digital thermometer or thermocouple with a thin probe for thin foods such as patties or fillets
- Some health districts set a routine check, such as at least once a week; follow your facility's policy
Common mistakes
- Using solid ice with no water.
- Reading before the mixture has settled at 32 F or before the needle stops.
- Touching the stem to the bottom or sides of the cup.
- Adjusting without repeating the check.
Practice this skill
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Sources and how we check them: How we verify.