Schonstedt Instrument GA.32 User manual

INSTRUCTION MANUAL
FOR
MODEL GA.32
MAGNETIC LOCATOR
SCHONSTEDT
INSTRUMENT
COMPANY

HelrFlux'
Locator
MODEL GA.32
SCHONSTEDT INSTRUMENT COMPANY
1775 WIEHLE AVENUE, RESTON, VIRGINIA 22090
Telephone [phone]

PREFACE
The Model GA-32 Magnetic Locator is a product of over twenty
years of experience in producing the world's finest flux-gate magnet-
ometers and magnetic detectors for aerospace, military and civilian
applications. The GA-32 incorporates the knowledge gleaned from
manufacturing under the most rigid quality control standards.
The heart of the GA-32 is its patented Schonstedt HeliFlux@
magnetic field sensors. These sensors, acknowledged to be the world's
finest, make possible the unequalled performance of the locator-
TABLE OF CONTENTS
OPERATION
I ntroduction
Turn-On and Range Setting
Search
Low Range
Extended Range
APPLlCATION NOTES
Basic Search Patterns
Strongly Magnetized Markers
Manholes, Septic Tanks, Wells, Pipes
Barbed Wire, Water, Snow
Along Fences
Valve Boxes
MAINTENANCE
Replacement of Batteries
Trouble Shooting Guide
CASE AND STRAP
SPECIFICATIONS
WARRANTY
1-3
I
1
2
3
3
4-9
4
o
7
8
I
10-1 1
10
11
12
13
14

OPERATION
INTRODUCTION
The Model GA-32 Magnetic Locator detects the magnetic field
of a ferromagnetic object. lt responds to the difference in magnetic
field between two sensors spaced about 20 inches apart. The response
consists of a change in frequency of a tone signal that is normally
present in the headphones.
The figure below illustrates an application of the locator in which it
is used to detect an iron marker for a property corner. In the illustration,
the magnetic field of the iron marker is stronger at sensor A than it is
at sensor B. As a result, the tone signal in the headphone has a higher
pitch than its normal idling frequency of approximately 65 pulses per
second.
Magnetic field of an iron marker.
TURN.ON AND RANGE SETTING
Connect the headphones to the iack on the underside of the
electronic unit. This turns the instrument on. Set the range control
knob on the underside of the electronic unit so the dot on the knob

OPERATION (cont.l
lines up with the dot on the case.
This position of the knob adjusts
the instru ment f or what is refer-
red to as NORMAL range, the
locator can be oriented in any
direction without producing a sig-
nificant change in frequency of
the tone signal from its idling rate.
In cold weather it may be neces-
sary to turn the knob slightly coun-
terclockwise bevond the dot to
achieve normal range. The converse
may be required for operation dur-
ing hot weather. Other range set-
tings are discussed in later para-
graphs.
Control setting
for normal range.
SEARCH
Grasp the locator just below the large end as illustrated be-
low. Because the upper sensor is located near where the locator
is usually held, wrist watches may produce unwanted tone frequency
changes. To avoid such problems either remove the wrist watch or
use the other hand. The earphones are magnetic so the locator should
not be operated closer than 24 inches from the headset.
To obtain maximum area coverage, the locator should be swept
from side to side with the small end of the instrument kept close to
the ground. A higher frequency tone will appear in the headphones
when the locator is within range of an iron marker.
ood
Searching with the locator.

OPERATION (cont.l
LOW RANGE
Unwanted backgrou nd signals due
to nearby magnetic objects may re-
quire that the range of the locator
be reduced. To reduce the range,
turn the knob in the clockwise direc-
tion from the reference dot. Reduced
range is useful in pinpointing the
location of a strongly magnetized
marker.
Control setting for low range.
o06'
EXTENDED RANGE
The range of the locator can be
increased by turning the range con-
trol knob counterclockwise from the
reference dot. The added range
imposes some constraint on oper-
ating methods. The locator tone
will vary in frequency depending
on the instrument's orientation in
the earth's magnetic f ield.
Control setting
for extended range
When searching using extended range, keep the locator in a fixed
orientation, preferably vertical and away from the headphones. Avoid
turning the locator about its long axis as this may produce signal vari-
ations arising from misalignment of the sensors. The presence of a
ferromagnetic object will be indicated by a change in tone frequency.
o0'6

APPLICATION NOTES
BASIC SEARCH PATTERNS
SIGNAL FOR A
VERTICALLY
ORIENTED
TARGET. GREATEST
OVER TOP
SIGNAL FOR A
HORIZONTALLY
OBIENTED TARGET,
GBEATEST OVER ENDS
After you have detected a signal,
you can precisely locate the target
to save digging over a wide area.
Simply hold the locator vertically
while moving it in an "X" pattern.
The peak signal occurs directly over
a vertical target, and over the ends
of a horizontal target.
Using the "X" pattern while
holding the locator vertically allows
precise location of small objects.
A P-K nail marker can be located so
it can be uncovered using a 1/2" star
drill.
A trick that helps if you find more than one signal, when you
should find only one, is to raise the locator a few inches. Any signal
that disappears is probably not the one you are looking for. The signal
from a rusty boltor other small item will drop much faster with distance
than the signal from a larger target such as a corner marker.
SIGNAL ABOVE GROUND
SIGNAL AT GROUND
CORNER MARKER

APPLICATION NOTES (cont.l
STRONG LY MAGNETIZED MAR KERS
Strongly magnetized markers at or near the surface may give
misleading information as to the location of the markers. The mag-
netic field of such a marker is illustrated below.
The heavy line in the figure represents the variation in tone fre-
quency obtained when passing the locator over the marker. In moving
the instrument from A to B, the tone frequency increases and then
suddenly decreases at B. From just beyond B the tone frequency in-
creases sharply, becomes very high over the marker and decreases just
before reaching C. From C to D, the pattern is the reverse of that
from A to B. lt is ovbious 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.
The phenomenon is explained by the fact that the loca-
tor 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.

APPLTCATION NOTES (cont.l
MANHOLES. SEPTIC TANKS, WELLS, PIPES
The magnetic field is strongest
at the edges of manhole @vers.
Under a resurfaced road, the man-
hole covers produce a very strong
field. Turn the sensitivity down all
the way, and you can easily trace
the edges of the cover.
The great length of a wellcasing
providesa strong field at the surface
that permits easy location.
The locator can be used to precisely locate the
metal handles or reinforcing bars on septic tank covers.
lron water and gas lines near
the surface can be traced in some
cases. Greater signals are obtained
at the joints, ends and bends in the
pipe.
--t
6

APPLICATION NOTES (cont.l
BARBED-WI R E, WATE R, SNOW
Examine trees for bench marks
and embedded barbed wire of old
fence lines. Hold the locator paral-
lel with the direction of the wire.
You may use the locator in
flooded areas - just keep the elec-
tronic unit out of the water.
You can often trace barbed wire
(of old fence lines) beneath the
surface. Even if the wire is only a
trail of rust, it can be detected near
the surface. Tip the locator a little
lower than usual - but not parallel
with the ground.
Snow poses no problem - just
thrust the locator into the snow as
deeply as necessary to locate the
target.
7

APPLICATION NOTES (cont,l
ALONG FENCES
Search in the vicinity of an iron-wire fence requires not only
reduced range but also some control over the orientation of the locator.
Position the locator substantially horizontal with its long axis approxi-
mately perpendicular to the fence. This orientation assures that the
upper sensor is kept away from the fence.
Search by moving the locator along the fence, keeping the end a
constant distance from the fence. When a point 1-5l8" from the end of
the locator is directly over the stake, the signal will drop abruptly as
shown below. Any variation in position will produce an abrupt rise in
the frequency of the tone.
i.:-
SIGNAL NULL WITH
LOCATOR AS SHOWN
+ F1-5/8"
il'

1.
2.
4.
APPLICATION NOTES (cont.l
VALVE BOXES
Both the valve and its casing,
when iron, provide strong magnetic
fields which make them easy to
locate. Plastic enclosures containing
magnets are easily located at depths
of 3 feet or more.
OTHER NOTES
Operation under power lines may introduce a garbling of the tone
signal. The garbling generally does not significantly affect the
detection capabilities of the instrument.
The GA-32 is ideal for locating water meters and utility shut-off
valves.
The locator is useful in many instances for detecting the presence
of reinforcing bars in concrete.
The instrument will not detect nonmagnetic materials such as
gold, silver, copper, brass, aluminum, snow, water, ice, etc.

MAINTENANCE
REPLACEMENT OF BATTER I ES
The GA-32 is designed and built to give trouble free operation.
Normally, maintenance is limited to occasional replacement of the
batteries. In the event that your locator does malfunction, we ask that
you referto the troubleshooting guide on the next page. This lists a few
possible problems that can generally be corrected in the field so that
you will be able to continue using the locator without interuption.
The GA-32 is powered by four C-cell batteries carried in clips
illustrated in the exploded view of the electronic assembly below.
Access to the batteries is obtained by removing the nut at the end of
the electronic unit followed by the case. The battery keeper is removed
by sliding towards the end.
The four batteries are connected in series. The proper polarities
for the batteries are shown on the clip assemblies. Occasionally opposite
contacts must be pressed toward each other to insure sufficient pressure
between the contacts and the batteries.
NE f ?!$Er(FHhbJp-)
r-----r\
- - il- t__{i-f-
rrFov /"^.. L*"
BATTERY LCASE
CLIPS
Exploded view of the electronic unit case.
SOLDEB LUG AENT AWAY
FROM AATTERY HOLDER
Headset Plugged ln
SOLD€B LUGS BENl OP€N
TOWAAO AATTERY EOLDER
MAY SHOAT HEBE
I NCOR RECT
Headset Out
10

MAINTENANGE lcont.l
GA-32 TROUBLE SHOOTING GUIDE
Symptom Possible Cause How to Check How to Fix
Dead Dead Batteries
Headset
Batteries Not Making
Good Contact
Power Switch Not
Making Good Con-
tact
Replace
Try replacement (one
half of a stereo set
will work)
Inspect visually. try
increasing pressure
ol terminals by hand.
With electronics cover
removed and headset
plugged in unit will
operate if you press
contacts closed by
hand.
Replace
Replace with cor-
rect monaural set.
Bend battery holder
so batteries will fit
tight. lf corroded,
clean terminals with
sandpaper.
Bend power switch
blade so that firm
contact is made with
headset plug inserted.
8e sure contacts open
when headset plug is
removed. See f igure
on oppostte page.
Intermittent Headset
Batteries Not Making
Good Contaa
Power Switch Not
Making Good Con-
tact
Range Control
Try replacement (one
half of a stereo set
will work)
lnspect visually, try
increasing pressure
of terminals by hand.
With electronics cover
removed and headset
plugged in unit will
operate if you press
contacts closed by
hand.
Tone will sound noisy
or will change abrupt-
ly when range control
is adjusted.
Replace with correct
monaural set.
Bend battery holder
so batteries will f it
tight. lf corroded,
clean terminals with
sandpaper,
Bend power switch
blade so that firm
contact is made with
headset plug inserted.
8e sure contacts open
when headset plug is
removed. See f igure
on opposite page.
Replace range control
potentiometer.
Short Battery
Life
Power Switch Con-
tacts Remain Closed
Battery Case Ter-
minals Shorted to
Battery Case
Inspect to be sure con-
tacts open when head-
phone plug is removed,
I nspect visually
Bend power switch
blade so contacts open
when headset plug is
removed. Contacts
must close when plug
is inserted. See figure
on opposite page.
Bend battery terminal
lugs away from bat-
tery case. See figure
on opposite page.
11

SEVEFIALWAYEi
Tcl USE THE STFIAP
WITHTHEMLG.I
MAG'NETIC LclCATclFI CASE
WEAR ACROSS
THE CHEST
LIKE THIS
TURN WINGNUTS COUNTER.
CLOCKWISE 18OO PLACE THUMB
IN HOLE AND PRESS.
TO LOCK CASE
CLOSE CASE AND TURN WING-
NUTS CLOCKWISE UNTIL YOU
HEAR LOCK SNAP INTO POSI-
TION.
SHIPPING
IF CASE IS TO BE USED AS SHIPPING
CONTAINER CLEAN AREA WHERE
SHIPPING LABEL IS TO BE ATTACHED
WITH ISOPROPYL {RUBBING} ALCO.
HOL.
oFl
WEAR
ACBOSS
THE CHEST
LIKE THIS
oFl
SHORTEN STRAP
-
BY FORIUilNG A SECOND
IOOP AT EACH END
ANtrI
WEAR
ACROSS
THE SHOULDER
LIKE THIS
TO OPEN CASE

SPECIFICATIONS
(Specifications subject to change without notice.)
Input Power: Supplied by four C-cell batteries ( 1% V each).
Battery Life: 50 hours of intermittent operation.
Output Approximate 65-Hz idle tone in headphones.
Tone frequency increases (or decreases) with
gradient-f ield intensity.
Power Switch: Power is turned on when the headphone jack
is plugged in.
Weight Approximately 3 pounds including head-
phones.
OperatingTemperaturet 0"F to 12O"F.
Length: 42 inches.
Waterproof Length: 34% inches.
Nominal Sensor Spacing: 20 inches.
Construction: Rugged, all solid state.
PATENTS
Manufacture licensed under the following Patents: United States: 2,916,696;
2,981.885; 3,894,2a3; 3.909,704; 3.961.245 and 3B77,O72. Canada: 637,963;
673,375 and 1,0O6.915. British: 1,446,741 and 1 ,446,742. France: 2,205,671.
Other United States and foreign patents pending.
13

STANDARD WARRANTY
The Schonstedt lnstrument Company warrants each instrument
of its manufacture to be free from defects in materiat and workman-
ship. Our liability under this warranty is limited to servicing or adjust-
ing any instrument returned to the factory for this purpose and to
replace any defective part thereof. Electron tubes, batteries, lamps
and fuses are specifically excluded under this warranty.
This warranty is effective for one year after delivery to the orig-
inal purchaser. As a condition of the warranty, the instrument must
be returned by the original purchaser, transportation charges prepaid,
and prove to our satisfaction to be defective. lf fault has been caused
by misuse or abnormal conditions of operation, repairs will be billed
at cost. Prior to repair in this instance, a cost estimate will be sub-
mitted.
Service or shipping information will be furnished upon notification
of the difficulty encountered. Model and serial number must be supplied.
14

s-247-7837