Informational Locating; Notes On Accuracy - RIDGID SeekTech SR-60 Manual

Informational Locating

The normal shape of a field around a long conductor such as a
pipe or cable is circular (cylindrical in three dimensions). When
over the center of a circular field, the operator can observe the
following indicators:
• Maximum Signal Strength.
• Maximum Proximity Signal (Line Trace Mode).
• Centered Tracing line with minimized distortion.
• Guidance arrows centered, agreeing with Tracing line.
• Minimum Measured Depth.
• Sound pitch and volume will increase until they maxi-
mize over the target utility.
Figure 66: Over a Circular Field
The experienced operator learns to "see" the ground situation
by knowing how the different pieces of information provided by
the SR-60 relate to each other. While a simple straightforward lo-
cate of a circular field is fast and easy, tracing a line which is near
other large conductors such as power lines, phone lines, gas
mains, rebar, or even buried scrap metal can lead to questions
which can only be correctly answered by taking all the available
information into account.
By comparing the Guidance Arrows, the Tracing Line, Signal
Strength, Signal Angle, Measured Depth, and Proximity Signal,
an operator can see which way the field is being distorted.
Comparing the field information with an educated view of the
ground, noticing where transformers, meters, junction boxes,
manholes, and other indicators are located can help in under-
standing what is causing field distortion. It is important to re-
member, especially in complex situations, that the only guaran-
tee of the location of a particular line or pipe is visual inspection,
such as by potholing.
Compound or complex fields will produce different indications
on the SR-60 that will show what is happening. Some examples
might be:
• Disagreement between guidance arrows, Tracing Line
and Distortion Indicator.
• Inconsistent or unrealistic Measured Depth signal.
• Fluctuating random indications (also caused by very
weak signal).
• Inconsistent Proximity Signal compared to guidance ar-
rows (Active or Passive Line Trace modes).
• Signal strength maximizing off to one side of the
conductor.
Generally, distortion is likely to be worse at higher frequencies,
compared to lower frequencies. This is due to the tendency of
higher frequency signals to "jump" to adjacent conductors. Large
iron and steel objects such as vault and manhole covers, trench
plates, structural supports, rebar and vehicles can significantly
distort even the lowest frequencies. In general, passive locat-
ing is more subject to distortion than active locating, especially
in regards to depth measurements. Power transformers, buried
and overhead power lines are a common source of strong distor-
tion. It may be impossible to get an accurate locate close to a
large power transformer.

Notes on Accuracy

Measured Depth, Proximity, and Signal Strength measurements
rely on a strong signal being received by the SR-60. Remember
that the SR-60 is used above ground to sense electromagnetic
fields emitted from underground lines (electrical conductors
like metal cables and pipes) or Sondes (actively transmitting
beacons).
Ridge Tool Company
SeekTech SR-60
Figure 67: Over a Distorted Field
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