Schonstedt Instrument GA-52Cx User manual

Instruction Manual
Model GA-52Cx
Magnetic Locator
Manufactured By
Schonstedt Instrument Company
100 Edmond Road
Kearneysville, WV 25430
[phone]
Fax [phone]
Web: www.schonstedt.com
E-mail: [e-mail]
Made in USA
Preface
The GA-52Cx Magnetic Locator is a product of over 60 years’ experience in producing the world’s
finest flux-gate magnetometers and magnetic detectors for aerospace, military and civilian
applications. The GA-52Cx incorporates the knowledge obtained from manufacturing under the
most rigid quality control standards. The heart of the GA-52Cx is its patented Schonstedt
HeliFlux™ magnetic field sensors. These sensors, acknowledged to be the world’s finest, make
possible the unequaled performance of our locators.
February 2017

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Table of Contents
SECTION I: OPERATION
Introduction .......................................................................................................................... 3
Turn-On, Volume and Sensitivity Settings ............................................................................ 4
Search Procedure.................................................................................................................. 4
SECTION II: APPLICATION NOTES
Basic Signal Patterns ............................................................................................................. 5
Strongly Magnetized Markers............................................................................................... 6
Locating Manholes, Septic Tanks and Well Casings.............................................................. 7
Locating Objects under Snow or Water ............................................................................... 8
Locating and Tracing Barbed Wire........................................................................................ 8
Searching Areas along a Chain Link Fence ............................................................................ 9
Locating Valve Boxes............................................................................................................. 10
Locating Cast-Iron Pipes........................................................................................................ 10
Locating Steel Drums ............................................................................................................ 11
Additional Applications......................................................................................................... 12
Other Notes .......................................................................................................................... 12
SECTION III: MAINTENANCE
Replacement of Batteries ..................................................................................................... 13
Troubleshooting Guide ......................................................................................................... 14
SECTION IV: SERVICE INFORMATION.......................................................................................... 15
SECTION V: SPECIFICATIONS....................................................................................................... 15
SECTION VI: PARTS DIAGRAM .................................................................................................... 16
SECTION VII: LIMITED WARRANTY.............................................................................................. 17
Important Notice
Schonstedt believes the statements contained herein to be accurate and reliable;
however their accuracy, reliability or completeness is not guaranteed.
Schonstedt's only obligation shall be to repair or replace any instrument proven to be
defective within seven years of purchase. Schonstedt shall not be responsible for any
injury to persons or property, direct or consequential, arising from the use of any
instrument.

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SECTION I: OPERATION
Introduction
The GA-52Cx magnetic locator detects the magnetic field of ferromagnetic objects. It responds
to the difference in the magnetic field between two sensors that are spaced approximately 20
inches apart. This difference is referred to as the “signal strength” throughout this manual and
is represented in the instrument by an audio tone.
Figure 1 illustrates an application of the GA-52Cx locator in which it is used to detect an iron
marker used for property line identification. As shown, the magnetic field of the iron marker is
stronger at sensor A than it is at sensor B. This creates a signal strength that is larger than zero
(which would occur when the field strength is the same at both sensors).
The audio response of the GA-52Cx is designed so that the frequency of the audio tone
increases as the detected signal strength increases. As a result, the frequency of the audio
output is higher than the idling frequency that exists when the signal strength is approximately
zero.
Figure 1: Detecting Magnetic Field of an Iron Marker

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Turn-On, Sensitivity and Volume Settings
Set the On-Off/Sensitivity Control to position 2 and adjust the Volume Control until the idling
tone reaches a desired level. The sensitivity of the unit can be increased (to detect smaller
objects at greater depth) or decreased (to detect larger objects at smaller depths) by adjusting
the On-Off/Sensitivity Control. Setting the Sensitivity Control to position 2 provides what is
referred to as the “Normal Operating Range.” Positions 3 to 5 increase the sensitivity; position 1
decreases the sensitivity.
The locator can be oriented in any direction without producing a significant change in the
frequency of the tone from its idling frequency.
When using headphones, the Volume Control has no impact on the output level of the audio
signal.
Figure 2: Sensitivity Set for Normal Range (position 2)
Search Procedure
Turn the instrument on, set the sensitivity control to position 2
(Normal Range), and grasp the locator as illustrated in Figure 3.
Because the upper sensor is located near where the locator is
usually held, wrist watches may produce unwanted changes in
the tone’s frequency. Remove your wrist watch or hold the
locator in the other hand. Keep the locator away from your
shoes since they may contain magnetic material.
To obtain the maximum area of coverage, the locator should be
swept from side-to-side. When the locator comes within range
of an object, you will hear an increase in the frequency of the
output signal.
Figure 3: Searching with the Locator

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SECTION II: APPLICATION NOTES
Basic Signal Patterns
Figure 4: Signals from Vertical and Horizontal Targets
After you have detected the presence of a target, hold the locator vertically and slowly move it
back and forth in an "X" pattern while listening to the audio response. The audio peak will occur
when the locator is directly over a vertical target, or it will occur over the ends of a horizontal
target. The "X" pattern, as shown in Figure 5, is ideal for pinpointing small objects. By using this
technique, a 1-1/4 inch PK nail buried up to 12 inches can be precisely located.
Figure 5: “X” Pattern Provides Precision Locating

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If you are looking for a corner marker and detect two or more signals in the same general area,
raise the locator several inches above the ground or decrease the gain setting. Any signal that
disappears when the locator is held higher or the gain is decreased is probably coming from a
smaller target. As shown in Figure 6, the signal from a rusty bolt or other small item decreases
faster with distance than the signal from a larger target, such as an 18-inch length of 3/4 inch
rebar that can be located at depths up to 9 feet.
Figure 6: Raising the Locator Eliminates Unwanted Signals
Strongly Magnetized Markers
A strongly magnetized marker at or
near the surface may provide location
information that is misleading.
The heavy line in Figure 7 represents
the variations in tone frequencies
when the locator is moved over the
marker. When moving the instrument
from A to B, the frequency of the tone
increases and then decreases suddenly
at B. From just beyond B the
frequency of the tone increases
sharply, becomes very high directly
over the marker and decrease just
before reaching C. From C to D the
pattern is the reverse of that from A to
B. It is obvious that the locator must
enter the B-C region. Otherwise the
marker might be assumed to be
between A and B, or C and D.
Figure 7: Signal Pattern from a
Strongly Magnetized Marker
This phenomenon is explained by the fact that the locator is sensitive to the magnetic field
components parallel to its long axis. At points B and C the field is perpendicular to the locator so
no high frequency is produced at these points.

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Locating Manholes, Septic Tanks and Well Casings
The magnetic field is strongest at the edge of a shallow manhole cover. You can easily trace the
edges of covers near the surface. The locating depth for manhole covers ranges up to 10 feet.
The great length of a well casing provides a strong field at the surface that makes it easy to
locate casings buried up to 18 feet deep.
Figure 8: Locating Manhole Covers Figure 9: Locating Water Well Casings
The GA-52Cx can be used to precisely locate the metal handles or reinforcing bars on septic tank
covers at depths of up to 4 feet.
Figure 10: Signal Pattern Provided by Septic Tank Covers

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Locating Objects under Snow or Water
The locator can be used in flooded areas, but keep the electronic unit out of the water.
Snow poses no problem. Thrust the locator into the snow as deep as necessary to locate the
target.
Figure 11: Locating Objects under Snow or Water
Locating and Tracing Barbed Wire
You can often trace barbed wire (from old fence lines) buried just beneath the surface. Even if
the wire is only a trail of rust, it can still be detected near the surface. Tip the locator a little
lower than usual (but not parallel with the ground).
First, examine trees for bench marks and bits of embedded barbed wire. Then hold the locator
parallel with the direction of the wire.
Figure 12: Tracing Barbed Wire from Old Fence Lines

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Searching Areas along a Chain Link Fence
Searching in the vicinity of a chain link fence requires a reduced sensitivity setting and some
control over the orientation of the locator. As illustrated in Figure 13, position the locator
horizontally with its long axis perpendicular to the fence. This ensures that the upper sensor is
kept away from the fence.
Figure 13: Searching in the Vicinity of a Chain Link Fence
Perform the search by slowly moving the locator forward along the fence while also moving it to
the right and to the left. As you move forward, this technique will allow you to search an area
several feet wide. Listen for an abrupt drop in the signal (as shown by the null in Figure 14) that
will occur when the lower sensor, located 1-5/8 inches from the end of the locator, is directly
over the stake. Any variation in the position of the locator will produce an abrupt rise in the
frequency of the signal.
Figure 14: Placement of Locator While Searching Along a Chain Link Fence

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Locating Valve Boxes
Both the valve and its casing, when iron, provide strong magnetic fields that make them easy to
locate. Plastic enclosures containing magnets are easily located at depths of 10 feet or more.
Figure 15: Locating Valve Boxes and Casings
Locating Cast-Iron Pipes
As illustrated in Figure 16, cast-iron pipes produce the strongest magnetic signals at their joints.
Figure 16: Signal Patterns Provided by Cast-Iron Pipes