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Calibrating a Food Thermometer

The use of a properly calibrated thermometer is essential in restaurant kitchens to ensure that foods are cooked to the proper temperature, are chilled rapidly or held at proper temperatures after cooking, and to help monitor the temperature of holding equipment. Comparison to a certified thermometer under laboratory conditions, while the best way to calibrate a thermometer, is not feasible for the restaurant operator. The instructions below are intended to assist with field calibration of bi-metallic probe type thermometers.

  1. Fill a large (16 oz.) styrofoam cup with crushed ice.  Add clean tap water to fill the cup and stir well.
  2. Insert a minimum of 2 inches of thermometer stem into the water without letting it touch the sides or bottom of the container. Wait at least 30 seconds.

  3. Keeping the thermometer stem in the water, hold the adjusting nut under the head with a wrench or suitable tool and turn the thermometer head so that the pointer reads 32° F. This will adjust the thermometer for the low range.

  4. Bring clean water to a boil in a pan, and following steps 2 and 3, adjust the pointer to read 211° F (adjusted boiling temperature for Mecklenburg County, NC).

  5. Recheck the thermometer at low temperature by following steps 1 through 3. If the thermometer cannot be adjusted to ± 2° F at both the low and high temperature ranges, the thermometer needs to be replaced.

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