DC Current Surface and Volume Resistivity - ASTM D257 - Test Method
The purpose of this method is to set a standard testing method for finding insulation resistance, volume resistance, and surface resistance of low conductivity materials. Note that this standard is for low conductivity materials only; moderately conductive materials should reference ASTM D4496.
This method is used to determine the surface or volume resistivity of a given insulating material with a DC current. The method outlines several methods by which one could determine the resistivity, including sprayed metal electrode, binding-post and taper-pin electrodes, flat metal plate electrodes, and silver paint electrodes.
Applications and Benefits
Lucideon provides quantitative results for the surface and volume resistivity of electrically insulating materials with direct current in compliance with ISO 17025, 10 CFR 50 Appendix B and 10 CFR Part 21 quality management system requirements to support ASTM D257 testing requirements for industry.
Form of Results
Reporting for D257 requires that all testing parameters be listed, this includes: a positive identification of every tested material, the shape and dimensions of each sample, the type and dimensions of the electrodes used, any pre-test conditioning, and the environmental conditions of the test (esp. humidity). A statement must also be included, alongside the measured and calculated resistivity or conductivity, stating whether the reported values are “apparent” or “steady-state” as defined in the test of the method.
Surface resistivity is reported in ohms per square (Ω per square) where square is a general measurement based on either the SI or imperial unit of interest, typically it is reported in the SI unit system with centimeters. Volume resistivity is typically reported in ohm-centimeters (Ω-cm). The results of this standard may also be reported in terms of conductivity, using the Siemen (S) which is the inverse of the ohm.
- Dielectric Breakdown Voltage of Insulating Liquids – ASTM D877
- Dielectric strength, constant, and dissipation factors for rubber tape – ASTM D4325, D4388.