The isolation resistance between isolated networks and earth is measured. To determine the isolation resistance, a DC voltage is applied to the isolated network. The areas to be measured must be conductively connected to each other. The leakage current is determined as the result. This is proportional to the isolation resistance. The isolation resistance is displayed on an analogue scale. A limit value is set with my potentiometer on the back. The minimum value of the isolation resistance to be set is derived from the national standards or ship classifications.
If the value falls below the limit value, it can be evaluated via a dry contact. At the same time, a red "ALARM" LED lights up. Readiness for operation is signalled by a green LED "RUN".