In a temperature calibration laboratory, uncertainty evaluation is an important means to measure the reliability of calibration results.
The sources of uncertainty are multifaceted. Firstly, there is the uncertainty of the measurement equipment itself, including the accuracy, resolution, stability of the thermometer and the output accuracy of the temperature calibrator. For example, a thermometer marked with an accuracy of ±0.1°C, its own measurement uncertainty will affect the calibration results. Secondly, there is the uncertainty of the measurement environment, such as temperature fluctuations, humidity changes, electromagnetic interference, etc. in the laboratory. Even in a laboratory with good temperature control, small temperature fluctuations may lead to uncertainty in the calibration results. For example, if the laboratory temperature fluctuates by ±0.2°C in a short time, this needs to be considered in the uncertainty evaluation.
Personnel operation is also a source of uncertainty. Different operators have different measurement habits and proficiency levels, which may introduce certain errors. For example, when reading the thermometer reading, some operators may read higher or lower. This requires reducing this influence through personnel training and standardizing the operation process, and considering the uncertainty component introduced by personnel operation in the uncertainty evaluation.
The choice of measurement method also affects the uncertainty. Different calibration methods have different uncertainty levels. For example, the uncertainty ranges of the fixed-point calibration method and the comparison method are different. When performing uncertainty evaluation, it is necessary to calculate the uncertainty brought by the method according to the relevant standards and mathematical models based on the adopted measurement method.
When evaluating uncertainty, the method of combined standard uncertainty is usually used, and the uncertainty components from various sources are combined according to certain rules. For example, first calculate the uncertainty components of various factors such as measurement equipment, measurement environment, personnel operation and measurement method respectively, and then combine them according to the law of uncertainty propagation to obtain the total combined standard uncertainty. Finally, the expanded uncertainty can be calculated if needed to more intuitively represent the confidence interval of the calibration results, providing users with more comprehensive and accurate calibration information, enabling them to better judge the reliability of the calibration results and apply them in practical work.