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4 Using the vLoc3-Pro
4. Using the vLoc3-Pro
4.1 Using the Receiver
Line Locating - Using the “Classic” Screen.
69.1
640Hz25dB
4.2 Passive Locating
NOTE
The compass indicator is not active during passive location.
Passive locating refers to the process of detecting signals that “naturally” occur on pipes and cables. These tend to fall into two
categories, radio signals and power signals.
Radio signals are created by low frequency radio transmitters. These are used for broadcasting and communications. They
are positioned throughout the world. As the frequencies are very low the signals tend to penetrate and hug the curvature of
the earth. When the signals cross a long conductor such as a pipe or cable, the signals are re-radiated. It is these re-radiated
signals that can be detected by the Radio mode.
Power signals are created by mains power running in the supply cables. These signals are 50 or 60Hz depending on country.
For instance, the UK is 50Hz power but in the USA has 60Hz. When electrical power is distributed throughout the network, some
of the power nds its way back to the power station via the ground. These stray currents can jump onto pipes and cables and
also create power signals. Note that there has to be electrical current owing to create a detectable signal. For instance, a live
cable that is not in use may not radiate a detectable signal. Also, a very well balanced cable, ie exactly the same current owing
in live and neutral, will cancel out and may not create a signal. In practice this is unusual as there is usually enough imbalances
in the cable to create a good detectable signal.
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