The DMOM-200 S3 is Vanguard’s fourth generation, microprocessor-based, true DC micro-ohmmeter. It is designed for testing EHV circuit-breaker contact resistances, bushing contact joints, welding joints, or for any low-resistance measuring application. This high current and very lightweight (19.8 lbs/ 8.9 Kg) micro-ohmmeter is designed to meet the IEEE C57.09-1999 (5.15) requirement for testing circuit breaker contact resistance.

The DMOM-200 S3 can accurately measure resistance values from 1 micro-ohm to 5 ohms. A 0.1 micro-ohm resolution is possible with current greater than 5A. The DMOM-200 S3 applies a selectable true DC test current from 1A to 200A to the resistance load to be tested. The DMOM-200 S3 controls the test current’s rise and fall rates. The test current rise and fall rate can be selected from 5 seconds to 10 seconds. An “Auto Test” mode is also available and can be initiated simply by applying the sense cables’ leads across the two points of interest in the current path. This feature is very convenient when measuring a sequence of several resistance values in a circuit breaker contact. The DMOM-200 S3 can also compare test results against preset limits and determine if a test passed or failed, and a “Pass” or “Fail” flag is displayed accordingly.