Insulation measurements

Your device is designed to monitor the IT system insulation and continuously measure R, which is the insulation resistance (kΩ)

The IM20 also measures C, which is the leakage capacitance to the distribution system (μF), and calculates the impedance Z_C (kΩ) associated with C.

R measurement accuracy

When measuring the insulation resistance R, a high degree of accuracy is not required because the aim is merely to detect a fault, which is identified by a very large decrease in the insulation value.

In practice, the level of accuracy remains good across the normal usage range. Although it deteriorates outside of this range, there should be no impact as far as the user is concerned.