Automation of measurements in the dclf laboratory of the CSIR NML

Abstract

At the end of 2005 it was decided that a number of measurements performed in the dc Low Frequency (dclf) Laboratory of the CSIR National Metrology Laboratory (CSIR NML) could benefit from automation. The measurements identified were typically highly repetitive, and being performed using measuring instruments that can be connected to a computer with relatively little effort. A number of commercial instrumentation automation software packages were evaluated, but these packages were found to be too expensive for the purposes of a National Metrology Institute, given the programming experience available to the dclf laboratory. The software packages described in this paper were all written in Borland Delphi. To date, the following measurements were automated: calibration of digital multimeters up to 6.5 digits; capacitance measurements of a single standard capacitor and decade capacitors; and ac power measurements of single and three phase sources and meters. The following measurements are in the process of being automated: RLC measurements (inductance, resistance, and capacitance); ac-dc difference measurements and resistor calibration result analysis. The approach followed, software structure, validation and implementation of the software will be discussed. As these software packages automatically calculate the uncertainty of measurement, some time will be spent on the algorithms used for this purpose