Why Should You Calibrate Your Thermocouple?

November 11, 2019

A thermocouple is a sensor tool used to measure temperature in various settings such as residential, scientific, and industrial. For this temperature sensor to work accurately and effectively, it needs to be calibrated regularly.

The Importance of Calibration

You may not realize it, but the process of calibration is one of the primary reasons why everything around you is operating safely and as it should be. All measuring devices, not just thermocouples, go through the calibration process, or the checking of a measuring tool for accuracy. The process also involves adjusting the device to ensure that it is aligned to a certain standard. Note that the accuracy of measuring tools can change due to numerous factors such as the age of the device.

Given how critical it is to collect accurate data, all measuring tools and equipment should not only be maintained properly but calibrated regularly. If you fail to do so, you are at risk of not getting truthful data which can significantly impact whatever process you are working on. For instance, if your industrial temperature sensors are not properly calibrated, they are practically useless since you have no way to be sure if they are measuring temperature correctly.

The Need to Calibrate Your Thermocouple

A thermocouple consists of a pair of wire legs made of distinct yet different metals - one is positive while the other is negative. These two wires are joined together at one end known as hot or measuring junction. The other end, however, is known as cold or reference junction. To take the temperature measurement, the hot or measuring junction end is the one exposed to the substance that needs to be measured, while the cold or reference junction is connected to a different temperature. Considering the temperature difference between the hot junction and cold junction, a difference in voltage can be calculated between the two wire legs at the cold or reference end.

The voltage used to identify the differences in temperature is generated along the entire length of the wires between the two junctions. The accuracy of the measurement voltage depends primarily on the homogeneity of each wire. This means that the wires must consistently composition throughout.

Unfortunately, thermocouple wires can lose their homogenous nature over time, particularly in industrial settings. This change is caused by several factors such as mechanical damage, exposure to chemicals, and exposure to excessive heat (above 200 degrees Celsius). When a section of the thermocouple wire is no longer homogenous, it can generate a different voltage, thereby causing inaccurate temperature measurement. To address this issue, thermocouples are subjected to regular calibration.

Thermocouples are calibrated by essentially comparing the device for calibration to another device with a proven accuracy. During this process of comparison, you can then identify your sensor device's error of margin. With this information, you can then properly measure temperature using your thermocouple. Calibration can be done in a laboratory under strict and controlled conditions or you can also carry out field calibration which is much quicker.

To maintain the accuracy and quality of your temperature readings, make sure that your thermocouples are calibrated regularly. Note that annual calibration is recommended by experts. 

RAM Sensors offers a range of calibration certification services. Request one today!