The ITS-90 and Thermometer Calibration Wherever possible, use reference temperature measurement equipment regularly calibrated by an accredited laboratory, e.g. NCSLPH “Thermometer Calibration Procedure”, The common theme with any thermometer comparison device that is used is that it must provide a method for the reference thermometer and test thermometer to be maintained at the same temperature. In my the next few posts I will continue to explore the science behind meaningful temperature measurement. Readily available and easy to use, Fahrenheit’s temperature scale quickly gained acceptance and is still in use today, primarily in the United States. Fill both beakers with distilled water about two-thirds of the way full. In most comparison methods, a stirred liquid bath or isothermal dry block is used as the measuring medium. One such device is the, , which is a hybrid device consisting of a portable block containing a small amount of liquid. reference thermometer used for calibration. And if a measurement isn’t meaningful, why even bother? The scale between the two fixed points was divided into 100 equal increments. The lowest point was the temperature of an ice and salt water mixture (0 degrees), the midpoint was a mixture of water and ice (32 degrees), and the third was human body temperature. Put it in a pot and then boil it. Meteorological Instrument Center Japan MeteorologicaJapan Meteorological Agencyl Agency Outline 1. These instruments can be used to calibrate Liquid-In-Glass, RTD, Thermistors, Thermocouples, and Bi-Metal Thermometers. However, calibrations provided by NIST using fixed point cells are incredibly accurate by most standards. The original Table of Contents and several Legacy sections are provided here as reference only. A thermometer consists of: The measuring element (resistor, thermocouple, etc.) You can also calibrate thermometers using the following methods. These fixed points were based on the intrinsic physical properties of certain pure materials, such as the boiling point of oxygen. Dry block devices should be scrutinized closely before use to ensure that they are of the proper dimensions and design. Test the device to be calibrated. I Thought this was Supposed to be an Article about Calibration, not History! The scale was refined again in 1968, 1976, and finally in 1990. Procedure: Collect materials listed above. ), Visual inspection of liquid-in-glass thermometers, Replacing mercury thermometers with safer alternatives, ASTM International, “ASTM E1502, Standard Guide for Use of Fixed Point Cells for Reference Temperatures,”, ASTM International, “ASTM E220, Standard Test Method for Calibration of Thermocouples by Comparison Techniques,”, Calibration of Temperature Block Calibrators (EURAMET/cg-13/v.01),”, Dedikov, Yu A., “International Temperature Scale,” Thermopedia, February 2, 2011, <, “History of Temperature,” Capgo, November 4, 2010, <, “Temperature Calibration with Isotech Block Baths,”, Preston-Thomas, H., “The International Temperature Scale of 1990 (ITS-90),”, Ruhf, Robert J., “A Lesson on the Arbitrary Nature of Thermometer Scales Using the Historical Case of the Creation of the Fahrenheit Temperature Scale,”. The first step in recording thermometer calibration data is to create a calibration log system. Thermometer Calibration Procedure. Proper Thermometer Use What to Do • Calibrate the thermometer as scheduled. The ITS-27 had six reference points. In fact, historical accounts claim that over 35 different temperature scales had been developed by the 18th century. In the 19th century, William Thomson (also known as Lord Kelvin) developed the Kelvin temperature scale, which is founded on the theoretical existence of absolute zero. Any thermometer that has been dropped or abused will be taken out of service until it has been recalibrated. “test thermometer”) is compared to a reference thermometer at certain temperatures within the range of use. Please try again. More commonly, thermometers are calibrated by use of a comparison method in which the thermometer being calibrated (a.k.a. Test the device to be calibrated. Primary standards laboratories, such as the National Institute of Standards and Technology (NIST), use fixed-point cells to calibrate thermometers, such as standard platinum resistance thermometers (SPRTs), in accordance with the ITS-90 scale. Throughout history, many units and scales of temperature measurement have been developed for various applications around the world. The ITS-90 contains 17 fixed reference points which are used to define the modern-day International Temperature Scale. These devices typically consist of a metal block supplied with a temperature regulator that is used to maintain a constant temperature. Achieving a specific temperature is a critical step for ensuring product safety and quality in many food processing operations. Thermometer calibration by the Comparison Method includes the following steps: Review the device to be calibrated. % Proper Thermometer Use What to Do • Calibrate the thermometer as scheduled. 1. Clean the thermo-hygrometer with a soft cloth, carefully check the sensor for any signs of dust or contamination. After his death, the human body temperature fixed point was replaced with the boiling point of water (212 degrees). Here is a calibration procedure for a thermometer with probe long enough to be inserted on a metrology well or temperature bath (a dry bath). Probe thermometer calibration should be listed as a regular activity in your Food Safety Plan. Follow by stirring the contents and allow them to sit for about three minutes. The ITS-27 had six reference points. The reference thermometer and test thermometer are placed into bored holes in the test block. Thermometer calibration by fixed-point cells is not only costly, but it is also excessive for most temperature measurement applications used in construction materials laboratories. At this temperature, water can exist in solid, liquid, and gas phases simultaneously. On this page. calibration procedure. Fixed point cells are available commercially, and are used as reference standards by some calibration agencies. Measurements are taken with both a reference device and the test thermometer, and the two results are compared. /Author (SScramlin) Any Operational Procedure: Calibration procedures for common equipment used by the CFIA Inspectorate. Calibration using ITS-90 fixed points is not perfect, however, and a small degree of measurement uncertainty is intrinsic to achievement of one of the fixed points on the ITS-90 scale. The reflected temperature setting may be called background We are likely, therefore, to see another update to the scale sometime within the next few years. Dry blocks, also called drywells or temperature block calibrators, did not become commonplace until the 1980s. For example, it is assumed that the metals and gasses used in the fixed point cells are one hundred percent pure. 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