The 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 Auto-Ohm 200 S3 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).

Dual Ground Option
With the Dual Ground option, the Auto-Ohm-200 S3 can also measure the circuit breaker contact resistance with both sides of the breaker bushing being grounded.

When a test current is applied to a circuit breaker with both sides grounded, some of the test current flows through the safety ground cables.

Using an external current sensor, the Auto-Ohm-200S3 measures and eliminates this current from
the total test current.

The Auto-Ohm then calculates the actual resistance value of the circuit breaker.