Measuring Depth (Tracing Modes); Clipping (Tracing Modes) - RIDGID SeekTech SR-20 Operator's Manual

• While tracing, the Proximity Signal and Signal Strength
should maximize, at the same place where the guid-
ance arrows center on the display. If this is not the
case, the utility may be changing direction or other cou-
pled signals may be present.
• Higher frequencies bleed over to adjacent utilities
more readily, but may be needed to overcome breaks
in tracer wires or go over insulating couplers. If the
line is ungrounded at the far end, higher frequencies
may be the only means to make the line traceable.
(See Informational Locating on page 27.)
• When using the transmitter inductively, be sure to
begin the locate about 30 feet (10m) away to avoid "di-
rect coupling" (also know as air coupling). This occurs
when the SR-20 picks up the signal from the trans-
mitter directly through the air and not from the line
being traced. An unrealistic Measured Depth read-
ing when over the line can also indicate air coupling is
occurring.
• When using Inductive Mode it is always possible to
move the transmitter to a different point along the tar-
get line. This will sometimes improve the circuit and
provide a better signal.
While tracing, the mapping display operates best under
the following conditions:
• The line is level.
• The SR-20 Locator is above the target utility elevation.
• The SR-20 antenna mast is held approximately verti-
cal.
If these conditions are not met, pay close attention to
maximizing Signal Strength.
In general, if the SR-20 is used in a zone over the target
line within a sweep area of about two "depths" of the line,
the map will be useful and accurate. Be aware of this
when using the map if the target or line is very shallow.
Measuring Depth (Line Tracing Modes)
The SR-20 calculates Measured Depth by comparing the
strength of the signal at the lower antenna to that at the
upper antenna.
Measured Depth is measured correctly in an undis-
torted field when the bottom antenna is touching the
ground directly above the signal source and the an-
tenna mast is vertical.
1. To measure depth, place the locator on the ground,
directly above the Sonde or the line.
2. Measured Depth will be shown in the lower left
hand corner.
3. A Measured Depth reading can be forced by press-
ing the Select Key.
4. Measured Depth will be accurate only if the signal is
undistorted and the antenna mast is held vertical.
Testing for the consistency of the Measured Depth read-
ing can be done by raising the SR-20 a known distance
(say, 12 inches (33 cm)) and observing whether the
Measured Depth indicator increases by the same amount.
Small variation is acceptable, but if the Measured Depth
does not change, or changes drastically, it is an indication
of a "distorted" field, or very low current on the line.
NOTE! In Active Line Trace or Passive Line Trace modes,
pressing and holding the Select Key will force a
Measured Depth reading and will force the Signal
Angle indicator to change to Current. If sound is
set on, it will also re-center the audio tone.
Current and Signal Angle Reading
The Current Strength (
( ) in the upper right corner of the screen will display
the current detected on the traced line, in milliamps,
when the angle to the center of the detected field is
less than 35° and the SR-20 crosses the center of the
field as sensed by the guidance arrows.
When moving across the center of the field the current dis-
play will retain the displayed current value until the guid-
ance arrows reverse again, at which point the current
value will be updated.
When the angle to the center exceeds 35°, the Signal
Angle indicator will display the angle to the center of the
detected field.

Clipping (Tracing Modes)

Occasionally the Signal Strength will be strong enough
that the receiver will be unable to process the whole sig-
nal, a condition known as "clipping". When this occurs,
a warning symbol
that the signal is particularly strong. If clipping persists,
remedy it by increasing the distance between the an-
tennas and the target line OR by reducing the strength
of the current from the transmitter.
NOTE! Measured Depth Display is disabled under clip-
ping conditions.
Passive Line Tracing
In passive mode, the SR-20 is looking for electromag-
netic "noise" that has found its way onto a buried utility
line by any available means. Electromagnetic signals can
get onto buried utility lines in a variety of ways.
The most common reason is by means of direct con-
nection to some signal source. All operating electronic de-
Ridge Tool Company
SeekTech SR-20
) and Signal Angle indicator
will appear on the screen. It means
!
15