UL 508 Standard Requires Automated Safety Testing of Electromechanical Components

For compliance to regulatory safety requirements, electromechanical component manufacturers must submit their relays and switches and other components to endurance tests that verify their reliability and safety.  Alvin Agustin of MET Laboratories’ Baltimore Safety Lab contributed an article this month to Test & Measurement World Magazine to describe a test setup of this type for standard UL508.  Following is a short summary of this article. 

UL 508, “Standard for Industrial Control Equipment,” specifies that the component under test turn on and off 6,000 times while loaded.  The test cycle is 1 second on and 9 seconds off.

MET Laboratories, a NRTL, uses a microcontroller-based test setup to drive a relay under test.  The relay under test is loaded per UL 508, which specifies type and level of load.

To keep on-off cycle data from filling the microcontroller’s memory, the data is transferred to a PC through a serial port.  There, the data can be monitored using terminal emulation software. 

Errors in the on state can indicate a bad contact; errors in the off state can indicate a fused contact in the relay.

By replacing the relay driver circuit with an actuator, the same test setup can be used to test switches.

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