Circuit Testing is the testing of electric circuits to determine and locate any of the following circuit conditions:
Circuit testing for complex systems often requires extensive automatic checkout gear to determine the faults defined above as well as many quantities other than resistance.
In cable testing, the first step in fault location is to identify the faulty conductor and type of fault. This is done with a continuity tester, such as a battery and flashlight bulb or buzzer (Fig. 1), or an ohmmeter.
The Varley-loop test is similar to the Murray-loop test except for the inclusion of the adjustable resistance R. The Varley loop is used for fault location in high-resistance circuits.
An alternating-current capacitance bridge can be used for locating an open circuit as shown in Fig. 3. One test terminal is connected to the open conductor and the other terminal to a conductor of known continuity in the cable. All conductors associated with the test are opened at a convenient point beyond audio oscillator supplies the voltage to the bridge, which is balanced by adjusting RB for a null as detected by the earphones. Measured ratio RA/RB equals the ratio of capacitances between the lines and the grounded sheath. Because each capacitance is proportional to the length of line connected to the bridge, the location of the open circuit can be determined from Eqn. (4).
|Top of Page | More Troubleshooting Articles | HOME|