Ductor comes from a trade name and is used generically for a low-resistance ohmmeter that injects a DC test current, often 10 to 200 A, and measures the voltage drop with separate sense leads in a four-wire Kelvin arrangement. It reads in micro-ohms and is used on breaker main contacts, busbar joints, cable lugs and earth connections, where a few tens of extra micro-ohms means a hot joint at full load.
Ductor the main contacts on breaker 4, if it's still over 80 micro-ohms we pull it for a contact dressing.
Also heard as
- micro-ohmmeter
- DLRO
- Ducter
Related terms
Insulation resistance test
DC test that applies a high voltage between conductors and earth and reads leakage resistance in megohms.
Switchgear
Assemblies of breakers, switches, fuses, busbars and enclosures that control and protect power circuits.
Megger
To test insulation resistance with a high-voltage DC tester; also the jobsite name for the tester itself.