Food Thermometers

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

2. 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

3. 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

4. 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

5. 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

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

7. 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

8. 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

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

10. 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

11. 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

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