The Vanguard Auto-Ohm-200 S3 applies a selectable true DC test current from 1A to 200A to the resistance load to be tested.
The Vanguard Auto-Ohm-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 30 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 Vanguard Auto-Ohm-200 can also compare test results against preset limits and determine if a test passed or failed, and a “Pass” or “Fail” fl ag is displayed accordingly.
Since a true DC current (with controlled rise/ fall time) is passed through the circuit breaker contact, no magnetic transient is induced into the breaker’s current transformers. This feature greatly reduces the risk of inductively tripping a breaker control (bus differential relay).