A guarded switching system for automatic selection of high value resistors under calibration

摘要

At IEN, a guarded switching system for automatic selection of high value resistors under calibration was developed and metrologically characterized. By means of this system it is possible to select and connect to the measurement system high value resistors in three terminals configuration. As a matter of fact, its guard system allows to reduce the effects due to all the dispersion currents, due to insulation resistances between the resistors under calibration and their shields and due to the switching and connection system (such as insulation resistances among connections, of cables and connectors used for resistors connections). This system utilizes some details of the device described in. The uncertainties that can be reached with the measurement system in connection with the scanner in the calibration of high value resistors and a compatibility test of measurement performed with and without the scanner, are also given.