Food Thermometers Calibrating Instant-Read Bi-metallic Thermometers Adapted from a presentation prepared by Hospitality & Tourism Management Purdue University

Bi-metallic Stemmed Thermometers The most common and versatile type Measures temperature through a metal probe with a sensor at the end Usually measure from 0°F to 220°F 50F to 550F NOT practical Must be capable of re-calibration Must have an adjustable nut Adapted from Purdue University, Hospitality & Tourism Management

Bi-metallic Stemmed Thermometers When selecting this type of thermometer, it should have: An adjustable calibration nut Easy to read numbered temperature markings A dimple to mark the end of the sensing area Accuracy to within ± 2°F (± 1°C) Adapted from Purdue University, Hospitality & Tourism Management

Rules For Using the Thermometer Keep the thermometer and its case clean Wash, rinse, sanitize & air dry after every use When measuring an item, insert probe through the thickest part of the item insert deep enough to pass the dimple or sensing area of the thermometer Calibrate regularly to insure its accuracy Adapted from Purdue University, Hospitality & Tourism Management

Adapted from Purdue University, Hospitality & Tourism Management When to Calibrate -- After dropping the thermometer If shocked by extreme temperature change Periodically, depending on frequency of use. Adapted from Purdue University, Hospitality & Tourism Management

Calibrating the Thermometer There are two basic acceptable methods Ice-Point Method Boiling-Point Method Adapted from Purdue University, Hospitality & Tourism Management

Ice-Point Calibration Method Fill a large glass with crushed ice Add tap water to fill glass, stir well Place stem into the ice water sensing area must be completely submerged and not touching the glass Wait at least 30 seconds until the indicator stops moving Adapted from Purdue University, Hospitality & Tourism Management

Ice-Point Calibration Method With the thermometer stem still in the water Hold calibration nut secure with pliers/wrenche Carefully rotate thermometer head Until the pointer reads 32°F __________________ (The plastic case that comes with some models has a “hex-hole” built-in - to use instead of a pliers or wrench.) Adapted from Purdue University, Hospitality & Tourism Management

Ice-Point Calibration Method Adapted from Purdue University, Hospitality & Tourism Management

Boiling-Point Calibration Method Bring clean water to a boil in a deep pan Place the thermometer stem into the boiling water sensing area must be completely submerged and not touching the glass Wait at least 30 seconds until the indicator stops moving NOTE: only use for thermometers that start reading above 32°F Adapted from Purdue University, Hospitality & Tourism Management

Boiling-Point Calibration Method With the thermometer stem still in the water Hold calibration nut secure Carefully rotate thermometer head Until the pointer reads 32°F the thermometer head so that the pointer reads 212°F __________________ (The plastic case that comes with some models has a “hex-hole” built-in - to use instead of a pliers or wrench.) Adapted from Purdue University, Hospitality & Tourism Management

Boiling-Point Calibration Method Adapted from Purdue University, Hospitality & Tourism Management