Measurement Resolution in Uncertainty Calculation with the GUM Method Approach: A LabVIEW Application

Abstract

GUM (Guide to the Expression of Uncertainty in Measurement) is a method used for calculating uncertainty in measurements. The method involves an uncertainty calculation approach which also constitutes a reference for the international ISO/IEC 17025 standard. In the GUM method, all uncertainties are expressed as standard uncertainty. An uncertainty may incorporate various components where impacts from multiple sources are taken into consideration. Resolution errors resulting from the sensitivity of the measurement equipment has a significant impact in the calculation of uncertainty. Sensitivity of an analog measurement device such as a multimeter depends on the resolution of the ADC it contains. Multimeters with 8-bit resolution ADCs are often used as measurement devices for sensor voltage values to be read once or several times. Factors such as high measurement resolution and reading errors by operators lead to an increase in uncertainty. Multiple data from a sensor or many sensors cause a significant increase in uncertainty, which results in a serious loss of time and labor. In order to mitigate said two factors which increase uncertainty in such cases, analog data needs to be converted to digital data at high resolution and transferred into computer medium. In this study, an D7714 analog/digital converter IC with 24-bit resolution has been used to transfer digital data into computer medium via myRIO 1950. A LabVIEW-based software has been developed to perform register settings for the AD7714 IC and to retrieve data at 24-bit resolution.