Schonstedt Instrument GA-52B User manual

Insfr.tctiotr
Nlgrnuarl
Model
GA.528
Uagnetic
IffT
SCHONSTEDT INSTRUMENT
//
JP\

|ms/rructionlulalrutg,l
ModelGA-528
MagneticLocator
MANUFACTURED BY
Schonstedt Instrument Company
1775 Wiehle Avenue
Reston, Virginia 2ZO}O
(703) 471_1050
TWX: 710-833-9880
FAX: [phone]
Printed May 1989

PREFACE
The Model GA-528 Magnetic Locator is a product of thirtylive years of
experience in producing the woild's finestflux-gate magnetometers and mag-
netic detecfors for aerospace, military and civilian applications. The GA-528
incorporates the knowledge gleaned f rom manufacturing under the most rigid
qual ity control sfandards.
The heart of the GA-528 is ifs patented Schonstedt HeliFluxa magnetic
field sensors. Ihese sensors, acknowledged to be the world's finest, make
possib/e the unequalled performance of the locator.
TABLE OF CONTENTS
OPERATION
lntroduction
TurnOn, Volume and Sensitivity Settings
Low Sensitivity
High Sensitivity
Search
APPLICATION NOTES
Basic Search Patterns
Strongly Magnetized Marke rs
Manholes, Septic Tanks, Wel ls
Barbed Wire, Water, Snow
Along Fences
Valve Boxes
Cast lron Pipes
Other Notes
MAINTENANCE
Replacement of Batteries
Trouble Shooting Guide
Service Information
SPECIFICATIONS
GA-528 REPAIR PARTS
WARRANTY/SH I PPI NG I N FORMATION
1-3
1
2
2
3
3
4-10
4
F
6
7
8
I
U
10
10-12
10
12
12
12
13
14

Operation
INTRODUCTION
The Model GA-528 Magnetic Locator detects the magnetic field of a fer-
romagnetic object. lt responds to the difference in magnetic field between two
sensors spaced about 20 inches apart. The response consists of a change in
the frequency of a signal that is emitted by a loudspeaker.
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 mag-
netic field of the iron marker is stronger at sensor A than it is at sensor B. As a
result, the f requency of the signal on the loudspeaker is higher than the idling
frequency,40Hz, which exists when the field is the same at both sensors.
I
Oae.^b
G
O
oo
a
€
'lO
-€j
a
a
O
ct
<t oo
O
d\ d tRoN nnanren c) :
o-/ o
Magnetic field of an iron marker.

Operation (cont.)
TURN-ON, VOLUME AND SENSITIVITY SETTINGS
SENSITIVITY
Contro ls ( N ormal Settings)
LOW SENSITIVITY
Turn on the Model GA-528
and adjust the volume level by ro-
tating the ON-OFF/VOLUME con-
trol in a clockwise direction untll
the idling tone reaches the level
desired. Position the SENSITIVITY
(range) control as shown in the
figure. With the knob in this posi-
tion, the sensitivity is set for what
is referred to as NORMAL RANGE.
The locator can be oriented in any
direction without producing a sig-
nif icant change in frequency of the
tone from its idling rate.
When headphones are used,
no variation in sound volume is
provided by turning the VOLUME
Control.
Unwanted background signals
due to nearby magnetic objects
may require that the range of the
locator be reduced. To reduce the
range, turn the sensitivity knob in a
counterclockwise direction. Re-
duced range is useful in pinpointing
the location of a strongly magnetized
marker.
Setting for Low Sensitivity
INCREASE
DECREASE
OFF POSITION
ON-OFF/VOLUME
?:z

Operation (cont.)
HIGH SENSITIVITY The sensitivity of the locator
is increased by turn ing the sensitivity
knob in a clockwise direction. A
h igh sensitivity setting imposes
some constraint on operating meth-
ods. The locator tone will vary in
frequency depending on the instru-
ment's orientation in the earth's
magnetic f ield.
Control Setting for High Sensitivity
SEARCH
Set the sensitivity control for normal operation and grasp the locator
just below the large end as illustrated. Because the upper sensor is located
near where the locator is usually held, wrist watches may produce unwant-
ed tone frequency changes. To avoid such problems either remove the
wrist watch or use the other hand. Also, avoid bringing the locator close
to your shoes, since they might contain magnetic material.
To obtain maximum area coverage, the locator should be swept from
side to side with the smallend of the instrument kept close to the ground.
A higher frequency tone will be heard from the loudspeaker when the
locator is within range of an iron marker.
When searching using extend-
ed range, avoid turning the locator
about its long axis as this may pro-
duce signal variations arising from
misalignment of the sensors.
The presence of a ferromag-
netic object will be indicated by a
change in tone frequency.
Searching With the Locator

Application Notes
BASIC SEARCH PATTERNS
r--l
oto . O o O
oooa)o
. o ! ?> -o A
SIGNAL FOR A
VERTICALLY
ORIENTED
TARGET GREATEST
OVER TOP
SIGNAL FOR A
HORIZONTALLY
ORIENTED TABGET
GREAIEST OVER ENDS
aAoO-O
iJ- oO
(t o
.2 g
aA
o
e.C>
@.
oo
o.
C>
A oo6o
oo
ab
4oa
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
t t'X" pattern. The peak signal occurs
.\r directly over a vertical target, and over
the ends of a horizontal tarqet.
Using the "X" pattern allows
precise location of small objects. A
1-114" P-K nail marker can be located
at depths from 4" to 8". lt can be un-
covered by using a 112" 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 dis-
appears is probably not the one you are looking for. The signal from a
rusty bolt or other small item willdrop much faster with distance than the
signal from a larger target such as a corner marker. An 1B-inch length of
3/4 inch pipe can be located up to 7 feet.
SIGNAL ABOVE GROUND
SIGNAL AT GROUND
o.o
"€
a---) ^O O o
O \>o o
o SMALLBOLT D oY s
oQ
o:oo
'O O a o o c) a
oo oo no o
O ll. oo
coRNERrj**.*l | - C).
o oo o u U "

Application Notes (cont.)
STRONG LY MAGNET IZED MAR KERS
Strongly magnetized markers at or near the surface may give mis-
leading information as to the location of the markers. The magnetic field
of such a marker is illustrated below.
The heavy line in the f igure represents the variation in tone f requency
obtained when passing the locator over the marker. In moving the instru-
ment from A to B, the tone frequency increases and then suddenly de-
creases at B. From just beyond B the tone frequency increases 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 obvious
that the locator must enter the B-C region. Otherwise the marker miqht
be assumed to be between A and B or C and D.
The phenomenon is explained by the fact that the locator is sensi-
tive 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.
SIGNAL PATTERN
z

The magnetic f ield is strong-
est at the edges of a shallow
manhole cover. Turn the sensi-
tivity down all the way and you
can easily trace the edges of
covers near the surface. Locating
depth ranges up to B feet.
Application Notes (cont.)
MANHOLES, SEPTIC TANKS, WELLS
The locator can be used to precisely locate the metal handles or re-
inforcing bars on septic tank covers buried up to 4 feet.
The great length of a well
casing provides a strong f ield at
the surface that permits easy
locating of casings buried up to
1 5 feet.
-Jt4:+er---Jk o 60 6
oo4;
w"" a'
Wzl:
OUTPUT SIGNAL
"2."_oouo-orJ.,'-'5 ".;"-.o^;=:7 o o ozi
Zo-. 'c l-[e : : o "^- 6 3-'. :,5 *.f3- o^.'1-"

Application Notes (cont.)
BARBED-WI RE, WATER, SNOW
You may use the locator in
f looded areas - just keep the elec-
tron ic un it out of the water.
Snow poses no problem
just thrust the locator into the
snow as deeply as necessary to lo-
cate the target.
.-o o -s O .
b: fT ei 'o-o -:
b" ll""? * o." o:
Examine trees for bench
marks and embedded barbed rnrire
of old fence lines. Hold the locator
parallel with the direction of the
wire.
-J*- -J*?**- J,r-
Oo(JooOe
"ooQao-
1 .oo
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 de-
tected near the surface. Tip the
locator a little lower than usual -
but not parallel with the ground.
-l+- -
*L-=*:rl*rl
o
O4
q
gct
Ho'Gq
*- -5o

Application Notes (cont.)
ALONG FENCES
Search in the vicinity of an iron-wire fence requires not only a re-
duced sensitivity setting but also some control over the orientation of the
locator. Position the locator substantially horizontal with its long axis
approximately perpendicular to the fence. This orientation assures that
the upper sensor is kept away from the fence.
Search by moving the
constant distance from the
the locator is directly over
locator along the fence, keeping the end a
fence. When a point 1-5/8" from the end of
t lre st
shown below. Any variation in position will produce an abrupt rise in
the frequency of the tone.
SIGNAL NULL WITH

Application Notes (cont.)
VALVE BOXES
Both the valve and its casing,
when iron, provide strong magnetic
f ields wh ich make them easy to
locate. Plastic enclosures contain-
ing magnets are easily located at
depths of 6 feet or more.
CAST IRON PIPES
Cast iron pipes produce the strongest magnetic signals at their joints.
Initial search is best done as follows:
1. Turn sensitivity to maximum.
2. Hold locator vertical approximately 1 -1-1 lzfeet above the surface.
3. Walk without turning or tilting the locator.
4. Mark the approximate locations of signal maximums.
5. Return to the marked area and probe near the surface for signal
maximums. To do so it may be necessary to reduce the sensitivi-
ty of the locator. Four-inch pipe can be located at depths up to
8 feet.
The exact location of pipe joints may be displaced slightly from the
point of maximum signal particularly on pipes oriented east-west.
1.1% FEET
-rL
B
"o
' o o I - O-o
.o, e I "b-
-11
#l
-11
-
Il
=-o o-QoJ6-='6 'ffi

OTHER NOTES
'1. A burbling sound indicates the presence of an energized power line. The
burbling is due to the alternating magnetic field associated with the
electrical current.
2. The instrument will not detect nonmagnetic materials such as gold, silver,
copper, brass, aluminum, snow, water, ice, etc.
3. Normally, telephone lines cannot be detected.
Maintenance
REPLACEM ENT OF BATTERIES
The GA-528 is designed and built to give trouble f ree operation. Normally,
maintenance is limited to occasional replacement of the batteries. In the
event that your locator does malfunction, we ask that you refer to the trouble-
shooting guide located on page 12. 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 interruption. As indicated, low voltage from weak batteries
may cause the speaker to emit an uncontrollable loud signal.
The GA-52B is powered by four C-cell batteries carried in a battery holder
illustrated in the exploded view of the electronic assembly below. Access to
the batteries is obtained by removing the two knurled nuts, and sliding off the
cover.
The four batteries are connected in series. The proper polarities for the
batteries are shown on the battery holder. Batteries must be remoyed and
installed in the order as shown in the illustration on the next page.
COVER
BATTERY HOLDER
KNURLED NUTS
Exploded View of the Electronic Unit Caver
10

Maintenance (cont.)
INSTALL FIRST
REMOVE FIRST
INSTALL FIRST
BATTERY KEEPER
(Screw need not
be removed)
COIL SPRING HERE
BATTERY BOX
TERMINALS COIL SPRING HERE
BATTERY BOX BATTERIES
HEADPHONE
JACK
BE SURE THAT THESE
TERMINALS DO NOT MAKE
CONTACT WITH EACH OTHER
COIL SPRING
11

GA.52B TROUBLE SHOOTING GUIDE
SERVICE INFORMATION
lf your locator needs service, please return it to the factory along with the
following information: Name, Address, where purchased, Date, and Descrip-
tion of Trouble(s). See shipping information on page 14.
Input Power:
Battery Life:
Output:
Weight:
Speciftcations
(Specif ications subject to change without notice.)
Supplied by four Gcell batteries (1-112 V each).
50 hours (lntermittent usage.)
Approximate 40 Hz idle tone in speaker. Tone
frequency increases (or decreases) with gradi-
ent-field intensity.
Approximately 3 lbs. (1.36 kg.).
Operating Temperature: 0 o F to i2O"F (-1 8 "C to 49 .C)
Overall Length: 42-5116 in. (107.4 cm.)
Waterproof Length: 3 4-i t2 in. (87.6 cm.)
Nominal Sensor Spacing: 20 in. (50.8 cm.)
Construction: Rugged, all solid state.
PATENTS
Manufactured under the following patents: United states: 2,916,6g6;
2,981,885; 3,894,283; 3,909,704; 3,961 ,245;3,g77 ,072; 4,110,68g; 4,161 ,56g;
4,163,877; 4,258,320', 4,388,592 and Design ZSSS52. Canada: 637,g63;
673,375; 1 ,006,915; 1,037,121; j,141,003 and 1,177,891. Great Britarn:
1,446,741; 1,446,742', 1,494,865 and 2,0i2,4308. France'. 2,205,671 and
81 12295. Germany: 25 51 968.0-09; 23 55 630; and 29 01 163. Japan:
1 ,595,1 27 and 1 ,413,844. Other patents pending.
Symptom Possible Cause How to Check How to Fix
Dead Dead batteries.
Batteries not making
contact.
Broken wires.
Replace.
Check for contacl
corrosion.
Visually inspect.
Clean contacts.
Resolder.
Intermittent Batteries not makino
good contact. Check for corrosion. Clean contacts.
No sound Speaker terminals
shorted to cover. Visual. Bend terminals.
Uncontrollable
screaming Weak batteries. Replace.
12

@y'
U)
F
OE
o-
E,
o-
IIJ
tr
dl
N
I
C'
e'a'
\E/

LIMITED WARRANTY
The Schonstedt Instrument Company (Schonstedt) warrants each
product of its manufacture to be free from defects in material and work-
manship subject to the following terms and conditions. The warranty is
effective for one year after shipment by Schonstedt to the original
purchaser.
our obligation under the warranty is limited to servicing or adjusting
any product returned to the factory for this purpose and to replacing any
defective part thereof. Such product must be returned by the original
purchaser, transportation charges prepaid, with proof in writing, to our
satisfaction, of the defect. If the 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 submitted. Service or ship-
ping information will be furnished upon notification of the difficulty
encountered. Model and serial numbers must be supplied by user. Bat-
teries are specifically excluded under the warranty.
Schonstedt shall not be liable for any injury to persons or property or
for any other special or sequential damages sustained or expenses
incurred by reason of the use of any Schonstedt product.
FOR SERVICE OR REPAIR
Please ship locator (in its case to):
Schonstedt I nstrument Company
1775 Wieh le Avenue
Reston, VA 22090
14

SCHONSTFDT NSTRUMENT COMPANY
1775 Wiehfe Avenue, Reston, Virginia 22090-5199
Phone [phone] . TWX 710 833-9880 e FAX [phone]
$279-0589