A thermocouple is a temperature sensor device used to measure a wide temperature range in various scientific, industrial and even household settings. In order to use thermocouples effectively to collect accurate data, it is important to perform calibrations on a regular basis. Pyramid offers calibration services including NATA Accreditation and NATA Traceable Accreditation. Contact us or call 1300 737 976 for instrument calibration.
What is calibration and why is it important?
In general, calibration is self-evident to ensure specific and accurate measurements, regardless of the measuring equipment used. Calibration defines the quality of measurements used by a particular device, since over time the results may change slightly as the device ages or is affected by a number of environmental factors.
To maintain a high level of confidence, you need an ongoing process of regular maintenance and calibration of your equipment. Otherwise, you run the risk of slight (or eventually large) fluctuations in the accuracy of the collected data, which can have wide-ranging practical implications that you need to actively avoid.
Why Calibrate Thermocouples?
A thermocouple is made of a pair of wires made of special but dissimilar metals and uses the "Seebeck" effect, or thermoelectric effect, to determine the temperature difference caused by a voltage measurement between these two electrical conductors. At one end is the "heat/measure junction", which is connected to the substance whose temperature needs to be measured. The other end connects to the "cold/reference junction", which is a substance with a known and easily measured reference temperature, and the wire here also connects to the copper wire that goes to the meter/display.
The voltage (millivolts/mV) used to determine the temperature difference is not actually developed at the metal junction but along the entire length of the wire between the hot and cold junctions. Measuring voltage is only accurate if each wire is perfectly uniform, meaning it has a uniform composition.
In many industrial environments, thermocouple wire tends to lose uniformity over time due to various factors including chemical exposure or mechanical damage such as bent wires. Certain types of thermocouple metals are also affected by exposure to temperatures above 200℃, while others are not as easily altered. This is important to note because if one part of the thermocouple circuit is uneven, it can cause different voltages to be produced, resulting in overall measurement error. Therefore, thermocouples need to be calibrated to ensure accurate temperatures.
With thermocouples, calibration specifically refers to the method by which one specific device is compared to another of known accuracy. By determining the error tolerance of the device, you will know how to correctly calculate the temperature from the voltage being measured. Typically, calibration is performed in a laboratory under carefully controlled and maintained conditions, however, on-site calibration can also be a quick and efficient way to check the quality of a measurement.
The importance of regular inspection of thermocouples cannot be overemphasized to ensure that thermocouples are properly and accurately calibrated to maintain correct, repeatable and high-quality temperature measurements. Pyramid recommends calibration every 12 months.
