How to check the electromagnetic relay? One way

The discussion focuses on methods to check electromagnetic relays, emphasizing the limitations of using an ohmmeter alone due to its low test current, which may not reveal contact faults such as corrosion, mechanical damage, or oxidation that manifest under load. Measuring contact resistance with an ohmmeter can indicate continuity but often fails to detect issues that appear only at higher currents. Testing relays under load using incandescent bulbs or specialized testers (e.g., Testboy) provides a more reliable diagnosis by simulating real operating conditions and revealing contact degradation through voltage drop or flickering. Visual inspection of contacts, especially in relays with transparent housings, is also important. The coil resistance should be measured first to confirm coil integrity. Some relays have gold or platinum-plated contacts to reduce oxidation and improve longevity. Thermal imaging is recommended for contactors and high-current relays to detect overheating contacts. The discussion also notes that relay failures can be intermittent and that testing in the actual circuit with appropriate load current is often the most effective method. The importance of understanding relay specifications, such as minimum or self-cleaning current, is highlighted for proper testing and maintenance.
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