insulation resistance (IR)
Insulation resistance(IR) is a measure of the quality of the insulation material between two conductors or between a conductor and the shielding. The insulation material essentially determines the insulation resistance. It is not so much the insulation thickness that is decisive, but the material properties.
Insulation resistance is measured according to IEC 60512-2.
- For cables, the insulation resistance depends on the length and is specified in ohms x m or giga-ohms x km. Its values should be 1 giga-ohm x km. Due to the length dependence, the insulation resistance decreases with increasing distances.
- For capacitors, the insulation resistance corresponds to the DC resistance measured between the two terminals. For film capac itors and ceramic capacitors, this resistance is expressed in mega-ohm microfarads. As the capacitance increases, the insulation resistance decreases. The leakage current can be determined by the ratio of the applied voltage to the insulation resistance.
- For printed circuit boards, the surface resistance, orSIR, is usually used. This resistance for insulating surfaces depends on the nature of the insulation material, but also on the contamination, corrosion, atmosphere and moisture absorption of the insulation material. VDE has specified insulation resistances ind VDE 0110.