Extech Instruments CB20 User Manual page 4

Setting Maximum Sensitivity
Before performing a scan, set the unit for maximum sensitivity. To maximize sensitivity: After
powering the unit ON, hold the unit away from the circuit breaker panel and then press and
release the reset button once.
Finding a Circuit Breaker
The transmitter injects a signal onto the circuit which can be detected by the receiver. The
receiver will beep and the indicating LED will change from red to green when the strongest signal
is located. The receiver sensitivity automatically adjusts to minimize false identifications.
Please follow the instructions below very carefully with regard to the orientation angle of the
sensor head to the circuit breaker area. Failure to follow these directions exactly could lead to
inconclusive test results; also note the accompanying diagram for additional guidance.
1. Plug the transmitter into the socket under test and the "correct" LEDs will turn on.
2. Go to the circuit breaker panel or fuse box and switch ON the receiver. The Indicating LED
on the receiver will light red to indicate automatic scan.
3. Place the sensing tip in contact with the
face of the circuit breaker or fuses. The
sensing tip must be flat against the circuit
breaker at all times during the test. Any tilt
in the angle, in one direction or another,
will affect the sensor's ability to pick up the
signal.
4. Slowly run the sensing tip along the row of
circuit breakers. Maintain a constant angle
to the breakers as shown. The frequency of
the beeping will increase to a very rapid or
continuous tone and the LED will turn from
red to green when the receiver encounters
the breaker with the strongest signal.
Continue the scan through all the breakers.
5. Repeat the scan of the row of breakers.
With each sweep the receiver will
automatically adjust its sensitivity and disregard weaker signals.
6. Continue scanning until the correct indication (rapid or continuous tone and green LED) is
given only when the sensing tip is over one breaker or fuse. This is the breaker protecting
the circuit that the transmitter is plugged into.
7. Turn the selected circuit breaker off and the receiver will revert to a red LED display.
8. Return to the tested socket and confirm that the correct breaker has been selected by
checking that the LEDs on the transmitter are no longer ON (power is off).
9. Press and Hold the ON/OFF/RESET button to turn the Receiver OFF.
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