Surface and contact resistance
The determination of surface and volume resistivity are important parameters for describing the electrical insulation behavior of insulating materials or the conductivity of electrically conductive plastics.
Depending on the conductivity of the material to be tested, different standards are applied: For electrically conductive materials (resistance < 106 Ω), DIN EN ISO 3915 is used to measure the specific electrical resistance of conductive plastics; for non-conductive materials, IEC 60093 volume resistivity and surface resistivity of solid electrically insulating materials is used.
The resistance to the flow of current through a material is called the volume resistivity or often simply the (electrical) resistance. It has the unit Ohm (1 Ω = 1 V/A). The surface resistance characterizes the influence of the material surface.
Plate-shaped test specimens are used to determine the resistance values according to IEC 60093. A constant DC voltage is applied to the test specimens by means of circular electrodes and the resistance is measured.
The test according to IEC 3915 is carried out on type 1A tension rods. The measurement is carried out using the 4-pole method in the so-called low-resistance method. In this test, a constant current is applied and the voltage drop is measured.