Schonstedt Instrument GA-52Cx User manual

- 1 -
Instruction Manual
Model GA-52Cx
Magnetic Locator
Manufactured By
Schonstedt Instrument Company
100 Edmond Road
Kearneysville, WV 25430
[phone]
Fax [phone]
Made in USA
Preface
The Model GA-52Cx Magnetic Locator is a product of over forty-five years of 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.
June 2003

- 2 -
Table of Contents
Operation Page
Introduction 3
Turn-On, Volume and Sensitivity Settings 3
Search Procedure 4
Application Notes
Basic Signal Patterns 5
Strongly Magnetized Markers 6
Locating Manholes, Septic Tanks and Well Casings 7
Locating Objects under Snow or Water 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 11
Other Notes 11
Maintenance
Replacement of Batteries 12
Troubleshooting Guide 13
Service Information 13
Specifications 13
Warranty and Shipping Information 14
Important Notice
Schonstedt believes the statements contained herein to be accurate and reliable. But their accuracy,
reliability, or completeness is not guaranteed.
Schonstedt’s only obligation shall be to repair or replace any instrument proved 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.

- 3 -
Operation
Introduction
The GA-52Cx Magnetic Locator detects the magnetic field of a ferromagnetic object. It responds to the
difference in the magnetic field between two sensors spaced about 20 inches apart. The response is a
change in the frequency of the signal emitted by the piezoelectric speaker.
Figure 1 illustrates an application of the locator in which it is used to detect an iron marker of the type 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. As a result, the frequency from the piezo electric speaker is higher than the idling
frequency, 40 Hz, which exists when the field strength is the same at both sensors.
Figure 1. Detecting Magnetic Field of an Iron Marker
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. 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 affect on the output level of the audio signal.
Figure 2. Sensitivity Set for Normal Range (position 2)

- 4 -
Search Procedure
Set the sensitivity control to position 2 (Normal Range) and grasp the locator as illustrated. Because the
upper sensor is located near where the locator is usually held, wrist
watches may produce unwanted changes in the tones frequency.
(Remove your wrist watch or hold the locator in the other hand).
Keep the locator away from your shoes, since they might contain
magnetic material.
To obtain maximum area 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

- 5 -
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 move it back and forth in an
“X” pattern. The peak signal occurs directly over a vertical target, and over the ends of a horizontal target.
The “X” pattern is ideal for pinpointing small objects. A 1-1/4-inch PK nail buried up to 12 inches can be
located so precisely with this technique that it can be uncovered using a 1/2-inch star drill.
Figure 5. “X” Pattern Provides Precision Locating
If you find more than one signal in the vicinity of a target, just raise the locator several inches higher or
reduce the sensitivity setting. Any signal that disappears when the locator is raised or the sensitivity is
reduced is probably not coming from the actual target. The signal from a rusty bolt or other small item will
decrease much faster with distance than the signal from a larger target such as a corner marker. An 18-inch
length of 3/4-inch pipe can be located at depths up to 9 feet.
Figure 6. Raising the Locator Eliminates Unwanted Signals

- 6 -
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 Ato B, the frequency of the tone increases and then suddenly
decreases at B. From just beyond Bthe frequency of the tone increases sharply, becomes very high directly
over the marker and decrease just before reaching C. From Cto Dthe pattern is the reverse of that from A
to B. It is obvious that the locator must enter the B-Cregion. Otherwise the marker might be assumed to be
between Aand B, or Cand 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 Band Cthe field is perpendicular to the locator so no high frequency is
produced at these points.

- 7 -
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. Locating depth 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

- 8 -
Locating Objects under Snow or Water and Tracing Barbed Wire
The locator can be used in flooded areas, just 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
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

- 9 -
Searching Areas Along a Chain Link Fence
Searching in the vicinity of a chain link fence requires a reduced sensitivity setting and also 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 in to the
right and to the left. This technique allows you to search an area several feet wide as you move forward.
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

- 10 -
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
The initial search should be performed as follows:
1. Adjust the sensitivity level for maximum.
2. Hold the locator vertically approximately 1 to 1-1/2 feet above the surface.
3. Walk along without turning or tilting the locator.
4. Mark the locations where the maximum signal levels occur.
5. Return to an area of maximum signal strength and hold the locator several inches above the surface.
The sensitivity will probably have to be reduced during this second pass. Four-inch pipes can be
located at depths of up to 10 feet.