Gas Measurement Systems Overall Uncertainty: Gas Meter Calibration Laboratories Case Study

One of the most important issues in accurate gas measurement is the uncertainty of the meter as the measurement tool. According to relevant standards and guidelines, it is necessary that the uncertainty of each component of the measurement system, such as the measurement element (e.g., orifice plate), temperature and pressure transmitter devices, etc., be within the permissible range. In addition, one of the very critical issues that unfortunately is not given much attention today is the overall uncertainty of the measurement system and the interactions and mutual effects of the system components on each other and on the overall uncertainty of the system. Therefore, this study presents the necessary relationships for calculating the overall uncertainty of gas meter calibration laboratories in the country. Finally, the overall uncertainty of two centers is calculated and reported as an example. One of these centers had the ability to calibrate turbine meters and the other had the ability to calibrate diaphragm meters. The results showed that the overall uncertainty of the turbine meter calibration center was 0.422%, of which the calibration deviation of the reference meter had the greatest role in this overall uncertainty. Also, the calculation of the overall uncertainty of the diaphragm meter calibration center showed that the best overall uncertainty of this center was 0.23%.