Vivax Metrotech vLocML2, Руководство пользователя

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9 Using the vLocPro2
Page 52 of 72
9.2 Passive or Active Location
There are two types of location method available with this system, they are:
9.2.1 Passive Locating
Passive locating is locating buried utilities using the electromagnetic signals that exist in the environment. We
group these under two settings:
•
Power (P) – these are signals that generally originate from electrical power generation systems.
These are around 50/60 Hz and their associated harmonic.
•
Radio (R) – these are signals that are generally originated by low frequency radio transmissions.
These are generally in the range of 16 kHz to 22 kHz.
Passive location is used to search an area to see if buried metallic lines are present (known as locating to
AVOID). It does not help to identify what buried pipe or cable is present, only to confirm that there is a pipe or
cable there. A typical application would be to check an area before installing a fence post.
9.2.2 Active Locating
Active locating is using a transmitter to apply a very precise frequency to a pipe or cable, and then using a
receiver turned to find the signal being radiated at that precise frequency. Active location frequencies can be
applied by direct connection, clamp or induction.
This receiver provides a wide range of frequencies for active location. Some will be the same as the
frequencies provided by the Vivax-Metrotech’s transmitter, others will be frequencies used in other
manufacturers’ transmitter.
The choice of frequencies when using induction or the clamp is restricted due to the requirement that these
modes be tuned for specific frequencies (or range of frequencies). The full range of frequencies is available in
“Direct connection” mode.
For frequencies below 45 kHz, authorities such as the FCC allow higher power output to be used; for
frequencies of 45 kHz and above, power output for this type of equipment is restricted to 1 watt. Therefore
more power is available when lower frequencies are used.