How to Calibrate Thermocouples

Calibration of a thermocouple in progress.
April 6, 2020

When you have a fever, you use a thermometer to decide how high your fever actually is. To keep temperatures constant in machinery, you have to use a different instrument to measure temperature. When industries use machinery, they have to measure temperatures that are very hot or very cold. That's where the thermocouples come in. Thermocouples use electric cables to measure temperatures in all different kinds of machinery. The cables, or wire legs, have two different kinds of metals to generate the electricity needed to measure extreme temperatures precisely.

Thermocouples are used as an instrument in many different kinds of industries. Power companies use them, as well as companies in oil and gas. Bio tech companies use thermocouples, and they are used in laboratory work in experiments. Nearly every industry uses thermocouples. They are also found in appliances you use every day, such as toasters, furnaces, and stoves.

Calibration of a Thermocouple

In order for thermocouples to work properly, they have to be properly calibrated. There are several different ways to calibrate a thermocouple. The most accurate way of calibrating a thermocouple is done over time in a laboratory. Scientists use fixed points within thermodynamics to calibrate these thermocouples. The laboratory method of thermocouple calibration is usually done when an absolutely accurate measurement needs to take place.

Another method of calibration for thermocouples is to do the comparison calculation method. In this method, thermocouples are still calibrated in a lab. The thermocouple is placed in a bath or a furnace, paired with a thermocouple that has already been calibrated. After the temperature is stabilized, the thermocouples are then compared.

Thermocouples can also be calibrated using a dry-block calculation method. Thermocouples can be inserted into a piece of machinery called a calibrator, which is a metal block with holes. The block is either heated or cooled to the temperature needed, and the thermocouples are then compared to the temperature of the metal block for accuracy.

How Often Does a Thermocouple Have to be Calibrated?

Most workers in business and industry calibrate their thermocouples at least once a year. However, there are times that these important pieces of machinery have to be calculated more often. You need to calibrate a thermocouple periodically so that it maintains its accuracy. You also need to recalibrate the thermocouple if it has been subjected to conditions that are unusual or unexpected. If you doubt a thermocouples performance, you may need to calibrate it again. 

If you calibrate your thermocouple, and the reading is off, it may be time to change it. If you've attempted to calibrate the thermocouple a couple of times, and it is still not measuring temperature accurately, it is time to replace it. There are other times you need to change the thermocouple, like if it is showing an open circuit. A thermocouple may also need to be changed when it shows low isolation from housing or from the sheath. If a thermocouple has been damaged, it needs to be replaced as well. When you look at a thermocouple, the sheath should be intact, and not showing signs of corrosion or oxidation.

Accuracy is extremely important for calibration, as it can reduce costs incurred by errors and ensure safety during industrial processes. RAM Sensors can provide certificates of calibration with the highest level of accuracy. Our experienced staff can offer suggestions and ideas to help meet your organization's calibration needs on wires, probes, and thermocouples. Contact us today!