During the thermocouple calibration process, there are inevitably various sources of error. Understanding these errors and mastering effective correction methods are crucial for improving calibration accuracy.
One common type of error is systematic error. This may be due to the inaccuracy of the calibration equipment itself, such as the deviation of the reference thermometer, the poor temperature uniformity of the calibration furnace or the constant temperature bath. Systematic errors have the characteristics of repeatability and predictability. They can be determined by comparison with a higher-precision standard device and corrected in the calibration results. For example, if a +0.5℃ deviation is found in the reference thermometer, this factor needs to be considered and adjusted accordingly when calculating the thermocouple error.
Random errors cannot be ignored either. They are usually caused by various random factors during the measurement process, such as small fluctuations in the ambient temperature, noise of the measuring instrument. Random errors are not repeatable, but their overall follows a certain statistical law. The influence of random errors can be reduced by taking the average value of multiple measurements. For example, multiple measurements are made at each calibration temperature point, and then the average value of these measurements is calculated as the final measurement result.
In addition, the characteristic changes of the thermocouple itself will also lead to errors. With the increase of usage time, the thermocouple wire may undergo oxidation, aging and other phenomena, thus changing its thermoelectric characteristics. This kind of error can be corrected by regular calibration and establishing the performance change curve of the thermocouple. Based on the usage history and calibration data of the thermocouple, predict its performance change trend and make compensation in actual measurement.
In summary, in thermocouple calibration, a comprehensive analysis of errors and the adoption of appropriate correction methods can significantly improve the measurement accuracy of thermocouples and ensure that they provide reliable temperature data in industrial and scientific research applications.
