Temperature calibration is the process through which a temperature-measuring instrument or device is adjusted to become more precise and accurate with its readings. There are different kinds of instruments used to measure temperature, the most common being thermocouple and resistive temperature detector.
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Sensors, transducers, thermometers and other instruments can all be calibrated. The calibrator is attached to the temperature sensing device and a test substance. The two most common types of temperature sensing devices are the thermocouple and the resistive temperature detector. The testing instruments measure the output of the device and compare it to the accepted standards. If there is a discrepancy, the non-calibrating instrument or device is adjusted until the margin of error is zero and both values are identical. Temperature calibration is necessary for the proper functioning of instruments and devices that require accurate and precise measurements for quality control and safety reasons. A temperature instrument that is not calibrated may display an incorrect reading which can be very dangerous whether the actual results are higher or lower than the reading. Temperature instruments are generally part of larger systems; decisions are made based on the reading provided by these instruments which is why they must be checked and calibrated. Calibration is used not only to adjust thermometers and sensors but is also performed on a wide range of equipment and machines as well as devices that measure speed, pressure and torque.
There are many reasons for temperature calibration. New instruments and devices are often calibrated before installed in a system. Other temperature instruments are calibrated after a certain period of time or usage has elapsed. Any shocks, vibrations or questionable results also warrant calibration. Temperature sensing instruments generally operate in similar ways to each other. A sensor in the tip of a probe expands or contracts according to the heat it encounters; the change is picked up and converted into an electrical signal that is then displayed on the screen of the handheld device. Or, in the case of thermometers, a fluid is subject to heat changes and, as it expands, it moves up through a glass pipe where the temperature can be read according to the height of the column. During calibration, the results from the probe or thermometer are compared to those of the device being tested. Another option is to bring the test device into contact with a substance or fluid of a known and standard temperature. A trained technician performs the calibration by attaching a device that is able to produce a correct reading to contrast the measurement of the machine. The technician who performs the calibration usually completes a summary report and certificate to show that the machine has been calibrated to industrial and national standards.
