Electrical Testing

Electrical testing measures the electrical behaviour of a product or material: insulation resistance, dielectric strength, leakage current, continuity, resistance, capacitance, surface and volume resistivity, tracking resistance.

The category serves two different purposes and they must not be confused. SAFETY measurements show that the user is protected against electric shock and sit within product safety standards. CHARACTERISATION measurements determine the electrical properties of a material or component and are used as design inputs.

For insulating materials the measurement is highly sensitive to the ENVIRONMENT. Surface moisture changes surface resistivity by orders of magnitude; insulation measurements are therefore made at defined temperature and humidity, usually after conditioning. The same specimen gives completely different results wet and dry.

The dielectric strength test appears in two different contexts and the two get confused: the TYPE test is applied once in product approval and is more severe; the ROUTINE test is applied to every unit on the production line at a level that will not stress the product. Presenting the production line test as a type test is incorrect.

Tracking resistance addresses a long-term failure mechanism on insulating surfaces: on a soiled and damp surface, small leakage currents form a conductive track over time. This is behaviour that does not appear in day-one measurements but can lead to fire in the field.