User guide

REV 3 DIGITMR USER’S MANUAL

1.2 Operational Modes

1.2.1. Quick-Shot Mode

In Quick-Shot (online) mode, the trip/close time is derived from the time of trip, or close-coil

initiation, to the breaker’s bushing current-break-or-make as detected by an AC clamp-on

current sensing probe. The DIGITMR can time a circuit breaker’s OPEN operation by sensing the

time when the OPEN coil is energized until the bushing CT current returns to zero. The breaker’s

CLOSE time is detected when the close coil is energized until the bushing CT current is detected.

The Quick-Shot mode provides a quick way to diagnose a breaker’s performance and can reduce

maintenance costs.

1.2.2. Time-versus-Travel Circuit Breaker Analyzer Mode

In Time-versus-Travel mode, the DigiTMR applies a test voltage of 35 Vdc to each of the contact

channels, thus allowing an analog to digital converter (A/D) to determine a close, open, or an

insertion resistor as the state of the contact. The DigiTMR records into memory 10,000 readings

from the A/D’s and the transducer position counters. The contact time, circuit breaker stroke

and velocity are then derived from the stored data.

The DigiTMR uses an up-down counter to sense the breaker’s transducer reading. The

DigiTMR’s travel transducer employs optical encoders to send quadrature signals to the

DigiTMR’s counters. With the use of digital transducers and counters, the need to setup or

calibrate the transducers is eliminated.

1.3 Supplied Cables

The DigiTMR comes furnished with the following cables:

• 1 Ground Cable

• 1 Power Cord

• 1 Contact Lead

• 1 Contact Extension Cable

• 1 Transducer Cable

• 3 Voltage and Trigger Leads

• 3 Voltage and Trigger Extension Cables

• 1 AC Current Transducer and Cable (Quick-Shot option only)

• 1 Initiate Cable

• 1 RS-232C cable