Volume resistance represents the resistance of an insulating material to leakage current through its body. Calculates the ratio of potential gradient to current in a material of the same density. The direct current resistance between the opposite surfaces of a cubic meter of material is numerically equal to the volume resistance in SI (Ohm-m).
Surface resistance is the resistance to leakage current across the surface of an insulating material. Two parallel electrodes, equidistant to the contact lengths, contact the surface of the material to measure the surface resistance. Therefore, the coefficient of the potential gradient (V / m) and the current per unit electrode length (A / m) indicate resistance. Lengths in surface resistance and section cancellation are usually measured in Ohms because the four ends of the electrodes form a square. However, some test results use Ohms per frame due to its more descriptive nature.
The resistance test measures the resistance of an insulator against leakage current by performing the following steps:
The final resistivity measurement depends on many external factors, including:
Applied Voltage: The amount of tension applied to the material greatly changes the final results of the test. To counteract this factor, sometimes it includes various voltages to create a test voltage dependency.
Electrification Time: The tested material is loaded at an exponential rate when exposed to voltage for a long time. Therefore, the resistivity of a sample increases over time during the test. This must be taken into account in order to make an accurate calculation.
Environmental Factors: Higher humidity levels create lower resistance compared to lower humidity levels. The conditions of the test environment have a major impact on potential results.
Because of these variables, these conditions should remain constant between tests when comparing multiple tests. ASTM standards recommend the commonly used 60V method for 500 seconds to make the results easily comparable. The results of this test can measure volume or surface resistance depending on their application.
Volume resistance represents electrical resistance through a cube of insulating material. It shows electrical resistance from one cubic centimeter of sample, as measured in ohms centimeters. Similarly, when using Ohm-inches, it shows electrical resistance from one-inch cube of material.
Electronic devices contain various chemicals to isolate or transmit. The volume resistance test for these chemicals allows electricity to pass through these components as intended. Determining the volume resistance of electrical consumer products is an important part of the safety standard test. In conductive pastes and other electronic components, the volume resistivity may indicate contamination if the desired resistivity or conductivity level is not reached.
Surface resistance describes the electrical resistance of a fixed surface length on the insulation material. This measurement does not take into account physical dimensions such as thickness and diameter. Since it only determines the resistance of the surface, only one physical measurement is required. Accordingly, the surface resistance between the electrodes is measured along the surface of the insulating material.
In material testing, this measurement can determine the surface resistance of plastics. In situations involving static electricity distribution, such as electronics production, low surface resistance is ideal. On their own, engineering plastics have a high level of surface resistance. Manufacturers often add carbon or surface treatment to increase conductivity. In general, the surface resistance test is rarely applied to metals as they already have high conductivity.
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