How to Re-Calibrate a Dial Thermometer

Water Method

A bimetal InstaRead dial thermometer may get out of calibration after years of use or after a particularly hard jolt. The hex nut on the underside of the thermometer is used to bring the thermometer back into calibration. First, you need a container of water at a known temperature — the closer to the mid-range the better. A fever thermometer is ideal for measuring the temperature of the water. Lacking that, ice water (which typically is at a temperature of about 34 F/1 C, not 32 F/0 C as many mistakenly believe) or boiling water (adjust for the altitude above 1,000 feet) can be used. Please be cautious around boiling water.

1. Immerse the thermometer stem in the water to a depth of at least 2 inches.

2. Hold the dial firmly (pliers or a wrench may have to be used) and slowly rotate the hex nut beneath the dial. Use the pliers or wrench to adjust the next nut. The pointer will start to move.

3. Rotate the nut clock wise to increase the reading. Rotate the nut counter clock wise to decrease the reading.

4. Stop adjusting when the pointer indicates the temperature of the water.


Using the Recalibration Tool on Sheath

1. Immerse thermometer in sheath in at least 2 inches of ice (34 F/1 C) or boiling water (212 F/100 C at sea level).

2. Adjust hex nut beneath dial with recalibration tool on sheath to 34 F/1 C or 212 F/100 C.