Volume Resistance Tests

Volume resistance tests are performed to determine the volume resistance of an insulation material. During testing, the surface fluxes of the sample are eliminated using an electrode.

Volume resistance represents the resistance of an insulating material to leakage current through its body. Calculate the ratio of the potential gradient relative to the current in a material of the same density. The direct current resistance between opposite faces of a cubic meter of material is numerically equal to the volume resistance in Ohm-m.

Surface resistance is the resistance to leakage current across the surface of an insulating material. Two parallel electrodes, equidistant from the contact lengths, come into contact with the surface of the material to measure the surface resistance.

The two international standards based on these tests are:

• ASTM D257-14 Standard of test methods for DC resistance or conductivity of insulating materials. Published by the American Society for Testing and Materials (ASTM), these test methods cover direct current procedures for the measurement of direct current insulation resistance, volume resistance, and surface resistance. From such measurements and the geometric dimensions of the sample and electrodes, both the volume and surface resistance of electrical insulating materials as well as the corresponding conductivities are calculated.
• IEC 60093 Standard of test methods for volume resistivity and surface resistivity of solid electrical insulating materials. Published by the International Electrotechnical Commission (IEC), this standard provides test methods and calculations for determining the volume and surface resistance of solid electrical insulating materials. Both the volume resistivity and surface resistivity tests are affected by the following factors: the magnitude and duration of voltage application, the structure and geometry of the electrodes, the temperature and humidity of the ambient atmosphere during conditioning and measurement, and the temperature and humidity of the samples.

Briefly, volume resistance and surface resistance tests measure the resistance of an insulator to leakage current by performing the following steps:

• Applying a known voltage to the material
• Recording the current created by the voltage
• Using Ohm's law to calculate the observed resistance
• Determination of the resistivity according to the physical dimensions of the sample

The final resistivity measurement depends on many external factors, including the applied voltage, electrification time, and environmental factors.

Our organization also provides volume resistance testing services among the numerous test, measurement, analysis and evaluation studies it provides for businesses in various sectors.