Most Common Reasons for Thermocouple Temperature Measurement Errors
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Thermocouples happen to be amongst the most well-known instruments for measuring temperature in the various types of industrial settings owing to their awesome versatility and easy usage. But thermocouple temperature measurement errors can still occur.
Most Common Reasons for Thermocouple Temperature Measurement Errors
Though these devices are quite reliable, thermocouple temperature measurement errors can always occur because of different causes. Let us discuss some of the most common reasons for such errors along with the solutions to rectify them:
- Choosing the Inappropriate Thermocouple Type on Transmitter: Different thermocouples like type K, type J, type N, type E, type T, type R, type S, & type B etc., are all designed differently to measure different temperature ranges, accuracies, electric outputs, and have different sensitivities. Using the wrong type of thermocouple can result in inaccurate temperature measurements, which happens to be a common error.
- Issues with the Thermocouple’s Extension Wires: The extension wire used to connect the thermocouple to the measurement device can introduce errors if it is of poor quality or not compatible with the thermocouple type. Factors such as resistance, insulation, and electromagnetic interference can affect the accuracy of the temperature measurement. If one accidentally reverses thermocouple lead wires’ polarity, then the temperature being measured would become wrong due to the difference in the temperatures of the 2 leads ends. The issue is very much fathomable as red is the usual colour for positive charges, however the red wire inside thermocouple’s cables usually has negative signal. Such coloration is in the thermocouples’ ANSI-standard, however it’s not what many people tend to expect.
- Innate Differences in the Alloys: Thermocouples rely on the principle of thermoelectric effect, where temperature differences generate voltage. However, there can be variations in the alloys used to construct thermocouples, which can result in inconsistent voltage outputs and measurement errors. Remember, no 2 batches of wires would be totally similar. As alloy percentages tend to vary during each process, errors in thermocouple accuracies tend to be inevitable.
- Variations in the Temperatures Around Reference Junction’s Connection: Thermocouples require a reference junction to measure temperature accurately. If the temperature at the reference junction deviates from the assumed value, it can introduce erroneous measurement of temperatures. Factors such as ambient temperature fluctuations and poor thermal contact can affect the reference junction temperature.
- Thermocouple Grounded at Multiple Locations: Grounding a thermocouple at more than one location can create additional thermoelectric junctions, which can introduce errors in the measurement. These additional junctions can generate unwanted voltages that interfere with the desired temperature measurement. If grounded at multiple locations, a “ground loop” could be formed with the current flowing through the thermocouple from 1 specific ground to another. This may tend to creäte electromagnetic fields that can cause radio-frequency-interference-related issues, which may tend to affect the measurement accuracy.
- Age of the Thermocouple: Over time, thermocouples can degrade due to factors such as corrosion, oxidation, or contamination. This can lead to changes in the thermocouple’s electrical properties, resulting in measurement errors. Regular calibration and replacement of aging thermocouples are necessary to maintain accuracy. Max temperature exposure, cyclic measurement, & frequency of cycles may tend to impact the metallurgy resulting in such a drift, which is mostly downwards. Sadly, such a drift can’t be forecasted, but 10-20 degrees F errors are quite common.
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Thermocouple temperature measurement errors are common. You can avoid running into losses by choosing your pick from a reliable vendor. Heatcon promises to give you the best-quality in this regard. So, make it your go-to purchase destination!
