When it comes to commercial walk-in coolers,
thermometers are your first line of defense in making sure your Walk-In
is functioning properly and holding its proper temperature. You
can help to avoid food spoilage and excessive food waste by making sure
your thermometer is calibrated correctly. Proper temperature also helps
decrease the chances of food borne illnesses.
When thermometers are shipped out to their respective buyers they are
often already calibrated to be within one degree of accuracy.
Unfortunately, the hustle and bustle of being transported to their
destination can cause calibration problems. It is best to check all new
thermometers for accuracy once you receive them by using the guide
below. In addition, if a thermometer is ever dropped it is wise to
calibrate it again to ensure it is reading temperatures correctly. There
is no strict regulation on how often you should calibrate your
thermometer but we recommend setting a regular calibration schedule
depending on how often your thermometer experiences large temperature
changes. These changes may happen when your cooler gets an extensive
cleaning or after a repair to your cooler is complete. If your cooler
stores food items it is best to calibrate your thermometer quarterly,
especially before any type of health inspections. Using the guide below
will help you easily calibrate your thermometer so that it can continue
to give you accurate readings.

USDA Guide To Calibrating Dial Thermometers:

1. Fill a large glass with finely crushed ice.

2. Add clean tap water to the top of the ice and stir well.

3. Immerse the probe of your thermometer a minimum of 2 inches into
the mixture, touching neither the sides nor the bottom of the glass.

4. Wait a minimum of 30 seconds before adjusting.

5. Without removing the probe from the ice, hold the adjusting nut
under the head of the thermometer with a suitable tool and turn the head
so the pointer reads 32 °F.

You can calibrate digital thermometers in a similar fashion to the steps above.
Some digital thermometers have a reset button or screw and this is
what you will adjust in order to get a 32 °F reading when your
thermometer is in ice water. Some people use a hot water method in order
to calibrate their thermometer. This method can lead to inaccuracies
when it comes to thermometers used in walk-in coolers
because boiling point changes depending on altitude and because walk-in
cooler thermometers are made to measure cold temperatures in the air.
Using the boiling water temperature method of calibration inherently
causes your thermometer to experience a large temperature change, which
can lead to calibration problems. Because of this, it is best to use the
ice water calibration method above.