GA-92XTd Magnetic Locator
Instruction Manual

Schonstedt Instrument Company
P: (800) 999 - 8280

100 Edmond Road, Kearneysville, WV 25430
www.schonstedt.com
schonstedt.inf@spx.com

Table of Contents
SECTION I: INTRODUCTION ............................................................................................. 3
SECTION II: OPERATING CONTROLS
ON/ Volume .............................................................................................................. 5
OFF .......................................................................................................................... 5
GAIN ........................................................................................................................ 5
SECTION III: VISUAL AND AUDIBLE INDICATORS
Gain Level ................................................................................................................ 6Battery Level ............................................................................................................ 6
Signal Strength and Polarity ..................................................................................... 6
SECTION IV: CONNECTORS AND ACCESSORIES
Headphone Jack ....................................................................................................... 7
Headphone Jack Plug ............................................................................................... 7
SECTION V: BATTERY REPLACEMENT ........................................................................... 8
SECTION VI: OPERATING RECOMMENDATIONS & APPLICATION NOTES
Search Procedure ..................................................................................................... 9
Basic Signal Patterns ............................................................................................... 10
Strongly Magnetized Markers ................................................................................... 11
Correct Stake Orientation ......................................................................................... 12
Locating Manholes, Septic Tanks and Well Casings................................................. 12
Locating and Tracing Barbed Wire ........................................................................... 13
Searching Areas along a Chain Link Fence .............................................................. 14
Locating Valve Boxes ............................................................................................... 14
Locating Cast-Iron Pipes .......................................................................................... 15
Locating Steel Drums ............................................................................................... 15
Locating Ordnance and Weapons ............................................................................ 16
Other Notes .............................................................................................................. 17
SECTION VII: SPECIFICATIONS ...................................................................................... 18
SECTION VIII: TECHNICAL SUPPORT ............................................................................. 18
SECTION IX: WARRANTY/SERVICE INFORMATION ...................................................... 19

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.

October 20182

SECTION I: INTRODUCTION
The GA-92XTd 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 9.5 inches apart. This difference is referred to as the “signal strength”
throughout this manual and is represented in the instrument by an audio tone, the display of abar graph, and a numeric indication. In addition, the polarity of the signal strength is shown
as a + or – sign on the display, and determines the side (right or left) on which the bar graphis displayed. Although most objects can be located using the audio indication alone,
simultaneous use of the audio and visual responses will provide additional information to help
you pinpoint a target and determine its orientation.
Figure 1 illustrates an application of the GA-92XTd locator in which it is used to detect an ironmarker used for property line identification. As shown, the magnetic field of the iron marker isstronger at sensor A than it is at sensor B. This creates a signal strength that is larger thanzero (which would occur when the field strength is the same at both sensors).
The audio response of the GA-92XTd 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 (~ 30 Hz) that exists when the signal strength isapproximately zero. The larger signal strength also causes the bar graph display to peak ineither the positive or the negative direction.

Figure 1: Detecting Magnetic Field of an Iron Marker

3The GA-92XTd unit can be operated either in the open or closed position and any position in
between (see Figure 2).

Figure 2: Open and Closed Positions
NOTE: In the closed position using non-lithium batteries, a slight signal may be detected in
the high gain settings even if no ferrous material is present. This can be avoided by 1)
decreasing the gain, 2) operating the unit in the extended position or 3) using a lithium
battery.
The GA-92XTd has an internal detent mechanism to keep the unit in either the fully extended(open) or fully retracted (closed) position. To extend the unit, grasp the looped end of thelocator and pull until the shaft locks into place. To return the unit to the closed position, push
the looped end back into the shaft. The unit will lock into place.

4

SECTION II: OPERATING CONTROLS
ON / Volume: To turn the unit on, push
this button.
Upon turn on, the volume
defaults to HIGH. Pushing the button asecond time changes the volume to
MEDIUM. Pushing the button a third time
MUTES the volume. Additional pushes of thisbutton cycle the volume through HIGHMEDIUM-MUTE.
OFF: To turn the unit off, push this button.

GAIN: The sensitivity of the unit canbe increased (to detect smaller objects atgreater depths) or decreased (to detectlarger objects at smaller depths) by adjusting
the gain up or down pushing the UP or
DOWN arrow buttons.

Figure 3: GA-92XTd Face Plate

5

SECTION III: VISUAL AND AUDIBLE INDICATORS
Gain Level Indicator: The gain range is indicated by a
4-segment LCD as shown in Figure 4: L (Low), M(Medium), H (High) and XH (Extra High). Upon turn on,
the gain defaults to M (Medium). Each press of the UP
or DOWN arrow buttons will cause the gain levelindicator to change accordingly.
Figure 4: Gain Level Indicators
Battery Level Indicator: The battery level is indicated by a 4-segment LCD indicator, as
shown in Figure 5. When all four segments are black, the voltage level is between 100% and75%. As the voltage decreases, the number of black
segments decreases. Battery life varies with usage andthe ambient temperature. Cold temperatures reduce
battery life. Low temperatures may result in only two or
three segments being black. This could be temporary,
and all segments will change to black as the temperature
increases.
Figure 5: Battery Voltage Status Indicators
Signal Strength and Polarity Indicator: The signal strength, defined as the difference (ordelta Δ) between the magnetic field detected at the top and bottom sensors, is shown as anumerical indication in mG (milligauss) units, is preceded by the polarity of the signal (+ or -),and is followed by the Δ symbol (to emphasize that it represents a “difference” between thetwo ends of the sensor array).
In addition, the signal strength is shown ina semi-circular bar graph, with more bars
indicating a stronger signal. Depending
on polarity, the bar graph will switch to the+ (right) or – (left) side. The signal
strength is also indicated by thefrequency of the audio signal; a higher
audio frequency indicates a stronger
signal.
Figure 6 shows the various visualindications of signal strength and polarity.

Figure 6: Signal Strength Visual Indications

6

SECTION IV: CONNECTORS AND ACCESSORIES

Headphone Jack: The headphone jack is located on the sideof the unit near the face of the locator. Headphones are
optional and may be purchased from Schonstedt as anaccessory. The headphone jack is monaural. Standard
stereo headphones may be used, but they will produce soundin only one ear. When the headphones are plugged in, thespeaker sound will be muted, but the ON/Volume button still
controls the volume of the headphones.

Figure 7: Headphones

Headphone Jack Plug: A Headphone Jack Plug has
been included with this product. It is recommended thatthe plug remain inserted into the jack any time that
headphones are not in use. This aids in making the
instrument more water-resistant.

Figure 8: Headphone Jack Plug

7

SECTION V: BATTERY REPLACEMENTThe GA-92XTd is powered by one 9-volt battery. The battery is located in the handle of the
instrument and can be accessed by turning the screw counterclockwise. To remove thebattery, tilt the unit so that the handle is pointing down, and the battery will slide out. Whenreplacing the battery, look at the outside of the battery door for the proper battery orientation.
As a safety measure, the unit will not turn on if the battery is not inserted correctly. You
should never have to force the battery door closed. If the battery does not seem to be goingin all the way, remove the battery, reverse its orientation and then replace it.

Figure 9: View of Battery Door and Compartment

8

SECTION VI: OPERATING RECOMMENDATIONS AND APPLICATION NOTES
Search Procedure
Turn the instrument ON. The gain defaults to Medium(M). Grasp the locator, as illustrated in Figure 10.
Since the upper sensor is located near the handle of the
instrument (especially if it is being used in the collapsed
position), wristwatches may produce unwanted changes
in the audio signal and in the meter indication.
Therefore, watches should be removed. Keep thelocator away from your shoes as they may containmagnetic material.
To obtain a maximum coverage area, sweep the locatorfrom side to side. When the locator comes within rangeof an iron object, the signal strength will peak, thefrequency of the audio signal will peak, the bar graph will
expand in the positive or negative direction, and thedigital readout will peak. This is shown in Figure 11.

Figure 10: Searching with the Locator

Figure 11: Illustration of Visual Indicators within
Range of an Iron Object

NOTE: The number of bars shown in the bar graph, thenumber displayed in the digital readout, and the frequencyof the audio signal will all depend on the signal strength,
which is affected by the type of iron object detected, itsorientation, and the gain setting.

9Basic Signal Patterns
When the GA-92XTd is positioned directly over a vertical target, the signal strength will peak
(audio signal, digital readout, and bar graph) at either a positive or negative polarity.
The audio signal, digital readout, and bar graph indications also peak over each end of ahorizontal target. One end is positive, the other is negative. This will help you to distinguishbetween two vertical pipes or one horizontal pipe. Usually two vertical pipes buried in close
proximity will produce bar graph indications with the same polarity.

Figure 12: Signals from Vertical and Horizontal Targets
After you have detected the presence of a target, hold the locator vertically and slowly move itback and forth in an "X" pattern while listening to the audio response and observing the bar
graph indicator. For a given gain setting, the number of bars will be greatest when the locatoris directly over a vertical target or the ends of a horizontal target. The "X" pattern, as shownin Figure 13, is ideal for pinpointing small objects. A 1-1/4 inch PK nail buried up to 10 inches
can be located precisely using this technique.

Figure 13: "X" Pattern provides Precision Locating
If you are looking for a corner marker and detect two or three signals in the same generalvicinity, raise the locator several inches above the ground or decrease the gain setting. Any
signal that disappears when the locator is held higher or when the gain is decreased is likely
coming from a smaller target. The signal from a rusty bolt or other small item (see Figure 14)10

is much weaker than the signal from a larger target, such as an 18-inch length of 3/4 inch
rebar which can be located at depths up to 8 feet.

Figure 14: Decreasing gain Eliminates Unwanted Signals
Strongly Magnetized Markers
A strongly magnetized marker that is at or near the surface will provide a weaker indication on
both sides of the marker, and that could be mistaken for the marker.
The heavy line in Figure 15 represents the increase and decrease in the audio and bar graphindications as you move the locator over a marker. Between points A and B, the signals
increase slightly and then decrease. Just beyond B, the signals increase rapidly, peakdirectly over the marker and then decrease at point C. From C to D, the signals increase anddecrease again. Therefore, if you do not move the locator completely across the marker, you
might assume that the weaker indication on either side of the marker is its location. The two
weaker indications occur because the locator is extremely sensitive to the magnetic fieldcomponents that are parallel to its long axis. At points B and C, the field is perpendicular tothe locator; therefore, no significant audio or bar graph indications are produced at thesepoints.

Figure 15: Signal Pattern from a Strongly Magnetized Marker

11Correct Stake Orientation
When placing stakes, correct orientation is important.
For checking purposes, the orientation of the pin relative to the locator is shown in Figure 16.
Check the pin with one orientation. Then rotate
the pin 180°. The orientation that gives the largest
reading is the one that should be used. Thisreading should be positive in the Northern
Hemisphere and negative in the Southern
Hemisphere.
An iron pin has two types of magnetization. One
is the magnetization induced by the Earth's
magnetic field. The induced magnetization isalways downward in the Northern Magnetic
Hemisphere and produces a positive output nomatter which end of the stake is driven into theground. The other type of field is the permanent
magnetization that is fixed to the pin.
Formaximum detection, the stake should be driven
into the ground such that the permanent
magnetization is in the same direction as theinduced magnetization.

Figure 16: Checking a Stake’s
Orientation

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 thesurface. Locating depths for manhole covers range up to 9 feet.

Figure 17: Locating Manhole Covers

The great length of a well casing provides a strong field at thesurface that makes it easy to locate casings buried up to 16 feet
deep.
Figure 18: Locating Water Well Casings

12The GA-92XTd can also be used to precisely locate the metal handles or reinforcing bars on
septic tank covers at depths of up to 4 feet.

Figure 19: Signal Patterns Provided by Septic Tank Covers
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 withthe ground.

Figure 20: Tracing Barbed Wire

Examine trees for bench marks and bits of embedded
barbed wire. Hold the locator parallel with the directionof the wire.

Figure 21: Tracing Pieces of Barbed Wire Embedded in
Trees

13

Searching Areas along a Chain Link Fence
Searching in the vicinity of achain link fence requires a
reduced sensitivity setting andsomecontrolovertheorientation of the locator. As
illustrated in Figure 22, position
the locator horizontally with its
long axis perpendicular to thefence. This insures that theupper sensor is kept away fromthe fence.

Figure 22: 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 theleft. As you move forward, thistechnique allows you to search
an area several feet wide.
Listen for an abrupt drop in thesignal (as shown by the null in
Figure 23) that will occur when
the lower sensor, located 1-1/2
inches from the end of thelocator, is directly over the
stake.
Any variation in theposition of the locator willproduce an abrupt rise in thefrequency of the signal.
Figure 23: Abrupt Drop of Signal while Searching
Along a Chain Link Fence

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 (which are typically used with non-ferrous valve boxes) areeasily located at depths of up to 9 feet.

Figure 24: Locating Valve Boxes and Casings14

Locating Cast-Iron Pipes
As illustrated in Figure 25, cast-iron pipes produce the strongest magnetic signals at theirjoints.

Figure 25: Signal Patterns Provided by Cast-Iron Pipes
After an initial sweep search identifies the general direction of the pipe, the steel pipe joints ortransition points can be more accurately traced by the following procedure:
1.
2.
3.
4.
5.

Set the Sensitivity control to maximum (XH indication).
Hold the locator vertically approximately 1 to 1-1/2 feet above the surface.
Walk without turning or tilting the locator.
Mark the locations where the maximum signal levels occur.
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 thissecond pass. Four-inch pipes can be located at depths up to 9 feet.

Locating Steel Drums
As shown in Figure 26,
the GA-92XTd's signal
patternwill
vary
depending on the verticalor horizontal orientation of
the drum and how deep it
is buried.
A fifty-five gallon drum
can be located at depths
ranging from 4 feet to 9
feeet.
Figure 26: Signal
Patterns Provided by
Steel Drums

15

Locating Ordnance and Weapons
The versatile, lightweight, cost-effective GA-92XTd is also designed to aid EOD technicians
and law enforcement officers during area search operations.

Figure 27: Basic Signal Patterns from
Vertical and Horizontal Targets Help to
Determine Target Orientation.

Figure 28: A 175mm Projectile can be located up to 3 feet deep.

Figure 29: An 81mm Mortar can be located up to 10 inches
deep.

Figure 30: MK81 Low Drag Bombs can be located up to 7
feet deep.

Figure 31: A discarded hand gun can be located up to 10
inches deep.

16

Other Notes
1. A burbling sound indicates the presence of an energized power line.
influence the meter indication unless it is associated with a magnetic structure.

This will not

2. The instrument will not respond to non-ferrous metals, such as gold, silver, copper, brass
and aluminum.

17

SECTION VII: SPECIFICATIONS(Specifications subject to change without notice)

Output:Audio: Signal increases or decreases in frequency with signal
strength (gradient field intensity). Audio frequency range: 30 to4000 Hz.
Visual: Expanding bar graph and +/- signs indicates polarity
and signal strength. Digital readout shows gradient field
intensity expressed in milligauss (mG). Range: 0 to 500 mG

Battery Indicator

4-segment LCD

Gain

4-Level LCD: Low (L), Medium (M), High (H), Extra High (XH)

Volume3 Levels: Muted, Medium and High

Input PowerOne 9V battery

Battery Life

24 Hours (intermittent usage)

Operating Temperature-13° F to 140° F (-25° C to 60° C)

Water and Dust Resistance

Rated IP54, when operated with earphone jack plug (provided)

Overall Length

Open: 26” (66 cm), Closed: 15.5” (39 cm)

Nominal Sensor Spacing

9.5” (24 cm)

Weight2.4 lb. (1.1 Kg)

Construction MaterialHigh impact ABS

SECTION VIII: TECHNICAL SUPPORT
Schonstedt offers technical support and sales support. For any reason regarding usage andapplication please contact our technical support team at 888-367-7014.

18

SECTION IX: WARRANTY / SERVICE INFORMATION
Limited Warranty:
Schonstedt Instrument Company (Schonstedt) warrants each product of its manufacture to be
free from defects in material and workmanship subject to the following terms and conditions.
The warranty is effective for 7 years* after the shipment by Schonstedt to the original
purchaser. Please complete the warranty registration card and send back to Schonstedt
Instrument Company.
Schonstedt’s obligation under the warranty is limited to servicing or adjusting any productreturned to the factory for this purpose and to replacing any defective part thereof. Suchproduct must be returned by the original purchaser, transportation charges prepaid, with adescription of the defect in writing. If the fault has been caused by misuse or abnormal
conditions of operation, repairs will be billed. Specifically, this warranty does not coverproduct that has been subject to inundation by fire, water or other liquid intrusion, or units thathave been damaged or compromised due to repair, alteration or modification by anyone otherthan an authorized repair representative. Prior to a repair being performed by Schonstedt, acost estimate will be submitted and no work will be completed until authorized by thecustomer. Batteries are specifically excluded under the warranty and should be addressed tothe manufacturer of batteries in question.
Schonstedt shall not be liable for any injury to persons or property or for any other special orconsequential damages sustained or expenses incurred by reason of the use of any
Schonstedt product.
* For Military & EOD applications, the warranty is 1 year.
Service Information:
If your locator needs service, please return it to the factory along with the following
information: Name, Address, Telephone, Fax number, Where Purchased, Date, and
Description of Trouble(s). An estimate will be provided prior to service work being done.

For Service or Repair
Please ship locator (in its case) to:
Schonstedt Instrument Company
100 Edmond Road
Kearneysville, WV 25430

Manufactured By

Schonstedt Instrument Company
100 Edmond Road, Kearneysville, WV 25430
Phone: (800) 999-8280
Fax (304) 725-109519