Fill a glass halfway with ice. Pour water into the glass to cover the ice.
Set the probe from the thermometer into the ice water and leave it there for one minute.
Remove the probe and read the temperature on the display. It should read 32 F. If the temperature is higher or lower than that, adjust your thermometer until it reads the correct temperature. Retest the thermometer after making adjustments to make sure it reads correctly.
Turn on the fryer and allow the oil to heat. Set the thermostat for the desired cooking temperature. Wait until the heating element has cycled on and off three times, to ensure the heat is stable at the desired temperature.
Wipe the thermometer to remove any water from the probe. Put on protective gloves.
Place the probe into the hot oil. Allow it to stay in the oil for 15 seconds, or until the numbers on the display stop changing.
Remove the probe and read the display immediately. If the oil is within 5 F of the desired temperature, don't do anything. If the display reads more or less than that, see a service technician to adjust your fryer to the correct temperature.