Know what the resistance number includes
The closed path is not only the volumetric resistance of the alloy; The narrowness of the contact surface, surface films, riveted or welded connection, terminal and test wire can also be seen in the number.
Precisely define the location of current application and voltage sensing points before comparing parts.
Common causes of high or unstable resistance
Contamination, oxide, insufficient force, misalignment, jump, arc erosion, metal transfer and thermal damage reduce the conductive surface.
A loose connection, poor welding or soldering, a cracked joint, and a hot terminal can also cause resistance outside the switching surface.
Use a controlled measurement method
For low resistances, Kelvin's four-wire method reduces the error of the wire and probe resistance. The instrument, fixture, contact force, probe location and test current must be constant.
Record temperature, number of cycles, stability time and repeatability of readings.
Use the icon to orient the review
Gradual increase can be caused by surface degradation, wear or power loss. Intermittent readings can indicate jumps, vibrations, contamination, or mechanical cracks.
Before changing the alloy, determine the exact location of heat and resistance on the contact surface, joint or terminal.
Build a failure analysis package
Keep the broken part as received as possible; Early cleaning can destroy evidence. Attach drawing, alloy batch, switching duty, cycle count, environment and clear pictures.
Confirm the corrective action in the full system
Alloy, geometry, connection method, contact force, thermal path and protection circuit must be validated together under inrush current and actual duty cycle.
Practical summary
Any alloy, geometry, or corrective action decisions must be verified by controlled drawing and representative testing on the final assembly.
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