RIDGID NaviTrack II - Manual (Page 16)

NaviTrack® II
15
Figure 24: High Probability Locate
CAUTION: Care should be taken to watch for signal interference
that may give inaccurate readings. Depth readings should be
taken as estimates and actual depths should be verified by
exposing the line before digging.
Using a Line Transmitter
In active Line Tracing, the NaviTrack® II works in conjunction
with an active line transmitter unit. There are three ways to
connect a line transmitter.
Direct Connection
The best way to connect a transmitter is usually by directly
connecting it (metal to metal) to one end of a target utility
pipe, trace-wire or cable, and sending the transmitted current
directly along the target.
Clamp Connection
Where direct connection is not possible, it is often possible to
fix an inductive clamp connector around the target conductor,
which energizes it inductively. To effectively induce a signal
using a clamp, the line must be metallic, and must have both
ends of the line grounded. (Signal can not be induced onto
a line in one direction unless current is able to flow in both
directions.)
Inductive Transmission
The transmitter can be used in an inductive mode without a
direct connection. This requires making sure the transmitter is
directly over a known segment of the target line and activating
the transmitter’s “inductive mode” which will illuminate the
line at a selected frequency.
NOTE: Refer to the manual provided with the transmitter
being used to ensure it is properly connected and grounded,
and set to the correct frequency.
Each of these methods has advantages depending on the
situation. Direct connection is usually most reliable in that the
signal is being applied directly to a known line; but situations
exist where induction may be the only option, or may work
better.
Passive Line Tracing
In passive mode the NaviTrack® II senses alternating current, or
AC fields generated by wires already carrying current, without
a transmitter being attached. Buried power lines typically do
not emit any traceable signal unless power is flowing in the
wires. For example streetlights that are turned off are hard
to trace passively. Due to coupling (either through induction
or through capacitance), all metallic lines in an area can be
energized passively. Because of this it is possible to locate lines
passively but it can be difficult to identify which line the locator
is tracing.
WARNING: In passive locating or when signals are extremely
weak, the depth will generally read too DEEP and the actual
buried depth may be MUCH shallower.
1. Select a Passive AC Trace Frequency with the passive
line trace icon.
Figure 25: 60 Hz Passive Trace Frequency
2. The NaviTrack® II has two passive AC tracing frequency
settings. They are 50 Hz, and 60 Hz. They are identified
with the power icon. The 50 Hz and 60 Hz respond to a
harmonic of commonly used AC frequencies. European
installations are typically 50 Hz.
When passive tracing, it is important to remember that T’s,
curves, other conductors in the vicinity, and nearby masses of
metal can add distortion to the field requiring closer scrutiny
of the data to determine the path of the target.
In general, passive tracing is the least effective option.