Ductor testing, also known as DLRO (Digital Low Resistance Ohmmeter) or contact resistance testing, is a critical diagnostic procedure used to measure the electrical resistance across the contacts and connections in circuit breakers and switchgear. Using specialized equipment like a ductor meter, we inject a high current (typically 10A or more) and measure the micro-ohm level resistance to ensure it's within manufacturer specifications (often <50–100 μΩ for most breakers). This test identifies issues like oxidation, corrosion, loose connections, or wear that increase resistance over time. At GFI Testing, we perform this as part of our NEMA-compliant breaker testing to verify reliable operation.
By minimizing risks such as overheating (which can lead to hot spots, melting, or fires), arcing during faults, energy losses, and unexpected breaker failures under load, ductor testing helps prevent catastrophic downtime, equipment damage, and safety hazards. High contact resistance can cause voltage drops, inefficient power distribution, and even contribute to arc flash incidents—making this test essential for NFPA-70E compliance and long-term system reliability in your California facility.