Thermometer Calibration Ice Point and Boiling Point Methods

Regulations � � � � Why calibrate a thermometer? Directives or standards such as ISO 9000 or ISO 17025 require organizations to provide accurate temperature measurements traceable to national or international standards. It is an important part of quality assurance in industry - for example in manufacturing to guarantee the quality of a product- and also to ensure effective testing or calibration by laboratories. Temperature is a critical measurement for ensuring the safety and quality of many food products. Whether monitoring temperatures at receiving, throughout production or final product storage and distribution, thermometer calibration is essential. The validation, verification reassessment section of the Hazard Analysis and Critical Control Point system stated in the Code of Federal Regulations (9 CFR 3: 417. 4) specifies that instruments used for monitoring critical control points must be calibrated. Choosing a thermometer: If your thermometer is not accurate within +/- 2°F of 32°F. , adjust thermometer accordingly. The ice point method permits calibration to within 0. 1°F. If your thermometer is not accurate within +/- 2°F of 212°F. , adjust thermometer accordingly. The boiling point method permits calibration to within 1. 0°F. Next Page Microbica Laboratory Partners, inc. © 2011 2

Ice Point Calibration 32 F +/-2 F � Use an insulated Cup for thermal stability ◦ We recommend a thermos over Styrofoam cups � Measure the cup height against your thermometer probe ◦ Probe should be at least one inch shorter than the cup � Place hole in center of thermos lid. Microbica Laboratory Partners, inc. (c) 2011 3

Ice Point Calibration 32 F +/-2 F � Add ½ crushed ice and ½ tap water (distilled preferred) � Allow to set for couple minutes � Place Thermometer probe in center hole � Slosh Ice-water to verify stability. � Readings 32 o. F +/- 2 o. F =Ok ◦ 32 o. F = 0 o. C � Prefer 32 o. F +/- 0. 1 o. F If the temperature is not at 32 o. F (0 o. C), then hold the calibration nut securely with a wrench and rotate the head of thermometer until it reads 32ºF (0 o. C). Follow manufacture’s instructions. Microbica Laboratory Partners, inc. (c) 2011 4

Boiling Point Calibration 212 F +/-2 F � Use a Pyrex cup or flask. ◦ Metal pot not preferred Fill cup 1. 5 inch below top. � Bring water to a slow boil. � Then place Probe in center of cup for 1 -2 minutes or until stable. ◦ Keep probe off bottom of cup � ◦ Use a non-metal support (safety) with vents/slots (keeps steam off dial) for visibility. And prevents loss of probe in hot liquid. ◦ Example: pasta scoop. • Water boils at 212 o. F (100 o. C) at elevations of sea level to 1, 000 ft. Microbica Laboratory Partners, inc. (c) 2011 5

Using a Dial Thermometer � Bimetallic Dial thermometers are sensitive only to about 2 inches from the tip. � Most have a ‘dimple’ indicator. Cut away view The full bimetallic part of this sensor must be immersed in the liquid (soup) or solid (meat) for accurate readings. Test ‘slim’ cuts or portions from the side for best results. Microbica Laboratory Partners, inc. © 2011 6

Calibration Adjustment � Dial: If the temperature is not at 32 o. F (0 o. C), Ice Point or 212 o. F (100 o. C) Boiling Point, then hold the calibration nut securely with a wrench and rotate the head of thermometer. Digital: Follow manufacture’s instructions. Microbica Laboratory Partners, inc. (c) 2011 7

Calibration Examples -Quiz Laboratory Calibration Boiling Flask, glass thermometer supported by clamp and stand Correct. Note: Thermometer centered and does not touch bottom Microbica Laboratory Partners, inc. (c) 2011 8

Calibration Examples -Quiz Boiling Point Calibration Boiling Metal Pot, with clipped thermometers. • Metal Pot and water not necessarily same temperatures • Does tip contact the pot or extend away? Not Preferred. Do not ‘cook’ thermometers during calibration. Microbica Laboratory Partners, inc. (c) 2011 9

Calibration Examples -Quiz Boiling Point Calibration Salad tongs not made to hold thin rods. Thermometer can slip out. Boiling Metal Pot, With metal tongs. Not Preferred. Note: Cooking method not good for calibration. Microbica Laboratory Partners, inc. (c) 2011 10

Calibration Examples -Quiz Ice Point Calibration Covered insulated cup, glass thermometer with clamp and stand. Never use glass thermometers with food. Acceptable Technique Avoid Styrofoam when possible Microbica Laboratory Partners, inc. (c) 2011 11

Calibration Examples -Quiz Ice Point Calibration Cubed Ice in water glass Not Preferred. Use

Calibration Examples -Quiz Ice Point Calibration Glass thermometer in ice NEVER USE GLASS THERMOMETERS

Calibration Examples -Quiz CALIBRATION SUMMARY Avoid Styrofoam cups. Save environment Pyrex cups work well for both Ice Point and Boiling Point Insulated Cups with plastic lids best for Ice Point Calibration Contact us at www. microbica. com Microbica Laboratory Partners, inc. (c) 2011 14