What is the measurement principle for determining insulation resistance with Sourcetronic insulation testers?

The resistance is calculated from the applied test voltage (which is floating and therefore suitable for measuring insulation resistance to ground in portable testers) and the measured leakage current. High voltage is applied to one end of the DUT. Between the other end and the instrument ground, a shunt resistor is inserted to measure current.

This configuration (current measurement in the return path) is commonly used – and is implemented in all our HV testers – as it avoids high voltages in the current measurement path and allows parasitic resistances to be eliminated by connecting the device ground to the DUT ground via the GUARD terminal (for portable devices only when not measuring insulation resistance to earth).

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