Evaluation of the measurement uncertainty during the calibration of teraohmmeters and insulation resistance meters

When preparing for accreditation, testing and calibration laboratories face the problem of developing methods for evaluating the measurement uncertainty. The interpretation of the Guide to the Expression of Uncertainty in Measurement regarding the calibration is given in the document of the European Cooperation for Accreditation. Despite the availability of guidance documents and publications on this issue, each evaluation case requires an analysis. The paper considers the calibration of teraohmmeters and insulation resistance meters, the feature of which is the lack of appropriate high resistance measures. Therefore, a resistance Y-network is used, which allows generating the reference resistance using three measures, which in turn causes additional components of the uncertainty. The analysis of the uncertainty components and the sensitivity coefficients of the deviation of indications to input values is conducted. The evaluation of the combined standard uncertainty and the expanded measurement uncertainty of the deviation of the calibration object indications is carried out, and the uncertainty budget is provided. An example of applying the developed method is given.