Dielectric Evaluation
High-voltage electrical testing evaluates the integrity of non-conductive materials within sensors and industrial cabling systems. Applying a standardized insulation resistance test reveals sub-microscopic pathways of leakage current that could cause instrument malfunction or electrical hazards. The measurement produces a resistance value expressed in megohms or gigohms, representing the quality of the dielectric barrier.
Measurement Procedure
Direct-current voltage is applied across the test specimen for a specified duration, typically sixty seconds, to allow capacitive charging currents to decay. This leaves only the steady-state resistive leakage current to be measured by the electrometer.
Environmental Distortion
Atmospheric humidity degrades the measured resistance by forming a conductive moisture film on the surface of the insulation. To isolate this surface leakage from the bulk resistance of the material, a guard terminal must be connected to intercept stray surface currents. Temperature also exerts an inverse exponential effect on resistance, requiring mathematical correction to a reference temperature of twenty degrees Celsius.
Instrument Calibration
Reference megohmmeter standards must be traceable to national laboratories to verify the accuracy of the applied voltage and current-sensing circuits. These standards employ precision high-value resistors that undergo periodic verification to ensure they do not drift beyond acceptable limits. Regular calibration of the test set ensures that industrial safety decisions rest on accurate measurement data.
