Schonstedt Instrument GA-72Cd User manual

Brand: Schonstedt Instrument

Model: GA-72Cd

Category: Measuring, testing & control

Type: User manual

Schonstedt Instrument GA-72Cd: This is a high-quality magnetic locator that will allow you to detect the magnetic field of ferromagnetic objects, such as iron markers used for property line identification, manholes, septic tanks, well casings, barbed wire, valve boxes, cast-iron pipes, steel drums, and even ordnance and weapons. It can even be used to locate objects under snow or water and trace the path of buried pipes or wires. The GA-72Cd has a patented HeliFlux® magnetic field sensor that provides superior sensitivity and accuracy.

- 1 -

InstructionManual



ModelGA‐72Cd

MagneticLocator



ManufacturedBy

SchonstedtInstrumentCompany

100EdmondRoad

Kearneysville,WV25430

(304)725‐1050

Fax(304)725‐1095



Web:www.schonstedt.com

E‐mail:info@schonstedt.com



Made inUSA



Preface



TheGA‐72Cd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‐72Cdincorporatestheknowledgeobtainedfrommanufacturingunderthe

most rigid quality control standards.The heart of the

 GA‐72Cd is its patented Schonstedt

HeliFlux



 magnetic field sensors.Thesesensors, acknowledged tobe theworld’sfinest,make

possibletheunequalledperformanceofourlocators.



June2017

- 2 -

TableofContents



SECTIONI:Operation

 Introduction.............................................................................................................................3

 Turn‐on,SensitivityandVolumeSettings................................................................................4

 BatteryLevelIndication...........................................................................................................4

 AudioOutputSelection............................................................................................................5

 SearchProcedure.....................................................................................................................6



SECTIONII:ApplicationNotes

 BasicSignalPatterns................................................................................................................7

 StronglyMagnetizedMarkers..................................................................................................8

 CorrectStakeOrientationisImportant...................................................................................9

 LocatingManholes,SepticTanksandWellCasings.................................................................9

 LocatingObjectsunderSnoworWater.................................................................................10

 LocatingandTracingBarbedWire.........................................................................................11

 SearchingAreas

alongaChainLinkFence.............................................................................11

 LocatingValveBoxes..............................................................................................................12

 LocatingCast‐IronPipes.........................................................................................................12

 LocatingSteelDrums.............................................................................................................13

 LocatingOrdnanceandWeapons..........................................................................................13

 AdditionalApplications..........................................................................................................15

 OtherNotes...........................................................................................................................15



SECTIONIII:DataLoggerOutput..................................................................................................16



SECTIONIV:Maintenance

 ReplacementofBatteries......................................................................................................17

 TroubleshootingGuide..........................................................................................................18



SECTIONV:ServiceandShippingInformation.............................................................................18



SECTIONVI:Specifications...........................................................................................................19



SECTIONVII:WarrantyInformation.............................................................................................20



SECTIONVIII:RepairParts............................................................................................................21



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.



- 3 -

SECTION1: OPERATION



Introduction



TheGA‐72CdMagneticLocatordetectsthemagneticfieldofferromagneticobjects.Itresponds

tothedifferenceinthemagnetic field between twosenso rs thatarespacedapproximately14

inchesapart.Thisdifferenceisreferredtoasthe“signalstrength”throughoutthismanualand

isrepresentedintheinstrument

by anaudiotoneand visualindicationofbothsignalstrength

and polarity.While most objects can be located using either the audio or visual indication,

simultaneoususeofbothwillhelpyoupinpointatargetanddetermineitsorientation.



Figure1illustratesanapplicationinwhichthelocator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.Asaresult,thefrequencyoftheaudiosignalishigherthanthe

idlingfrequency,40 Hz,whichexists when

thefieldstrengthis thesameat bothsenso rs.This

stronger signal also causes the digital indication to peak in either the positive or the negative

directionwhentheaudiosignalisatitshighestfrequency.



Figure1:DetectingMagneticFieldofanIronMarker



When shipped, the locator is

set to provide an audio signal that is heard as long as the

instrumentisturnedon.Ifdesired,youcanchangethissettingtoanaudiosignalthatisheard

onlywhentheinstrumentiswithindetectionrangeofanobject(refertopage5ofthismanual

forinstructions).



- 4 -

Turn‐On,SensitivityandVolumeSettings



Turn on the GA‐72Cd by rotating the On/Off‐Sensitivity control knob clockwise to position 1.

This sets the sensitivity to what is referred to as the Normal Range (the L meter indication).

Sensitivity can be increased by rotating the Sensitivity control clockwise to select

 M, H, or XH

settings(asindicatedon the meter’s GAINdisplay).Adjustthe Volume controlforthe desired

audiooutputlevel.



 ON/OFF HeadsetJack

 Sensitivity (alsooutputfor

 Levels DataLogger)



 VolumeControl



 MagneticField SignalStrength

 Polarity (indifferentialmilligauss)



 Selected

Sensitivity BatteryCharge

 Level Indicator

 Indicator



 NegativePolarity PositivePolarity

 ExpandingBarGraph ExpandingBarGraph



 Figure2:ControlandMeterIndications



BatteryLevelIndication



The meter’s BATT indicationdisplays the batteries’voltagelevel.When all four segments are

black,thevoltagelevelisbetween100%and25%(upto40hoursofoperationwithintermittent

usage).Asthevoltagedecreases,thenumberofblacksegments

decreases.Batterylifevaries

with usage and the 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backtoblackasthetemperatureincreases.



100 to 25% 25 to 20% 20 to 10% 10 to 1%



Figure3:BatteryVoltageStatusIndications

- 5 -

AudioOutputSelection



AllGA‐72CdsareshippedfromthefactorywiththeAudioOutputSwitchsetto“B”;thissetting

provides an audio signal that is always present.If you prefer to not hear a signal until the

locatoriswithindetectionrangeofatarget,settheswitch

to“A”.



AudioSignalwithOutputSwitchsetto“A”



No audio signal is heard until the GA‐72Cd comes within detection range of a

ferromagneticobject.Thelocatorwillincreaseinvolumeovertheobject.Itwill

decreasesinvolumeandturnoffwhenthelocatorismovedout

ofrange.



NOTE:If you put the GA‐72Cd down without turning the Sensitivity/Power

switchtoOff,the“power‐onmonitoring feature”(designedtoconserve battery

life)willinitiateabeepingaudio‐alertsignalafter15seconds.



AudioSignalwithAudioOutputSwitchsetto“B”



Asyoumovethe

GA‐72Cdacrossaferromagneticobject,the40Hzidlingsignal,

which is always present, increases in frequency, peaks when the locator is

directlyovertheobjectandthendecreasesto40Hz.



Regardless of which switch setting, the indication of signal strength and the polarity on the

meterwill

alwayspeak (positiveor negative) whenthelocatoris directlyovera ferromagnetic

object.



As shown in Figure 4, the cover must be removed to change the setting of the Audio Output

Switch.



Figure4:LocationofAudioOutputSwitch

- 6 -

SearchProcedure



Set the On/Off‐Sensitivity control for L and grasp the locator

asillustratedinFigure5.Becausetheuppersensorislocated

near where the locator is usually held, wrist watches may

produce unwanted changes in the audio signal and in the

meter indications. Remove your wrist watch or

 hold the

locator in the other hand.Keep the locator away from your

shoes;shoes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 iron object, the audio signal will peak,

the bar

graphwillexpandpositiveornegative,andthedigitalreadout

willpeak.



Figure5:SearchingWiththeLocator



WhentheGA‐72Cd is positioned directly over a verticalpipe, the audio and digital indications

will peak.The expanding bar graph and digital readout may display either a positive

 or a

negativelevel.

 ‐or+‐ +



 AudioSignal



Figure6:TheMeter’sPolarityIndicationsHelptoDetermineTargetOrientation



Theaudiosignal,bargraphanddigitalindicationspeakovereachendofahorizontalpipe.One

endispositive;theotherendisnegative.Thiswillhelpyoutodistinguishbetweentwovertical

pipes oronehorizontal pipe.Usually

twovertical pipes buried in closeproximitywillproduce

digitalindicationswiththesamepolarity.

- 7 -

APPLICATIONNOTES



BasicSignalPatterns



 Audiosignalpeaks Audiosignalpeaksovereachend

 directlyoververtical ofahorizontaltarget.Visualindications

 targets.Visualindications peakpositiveoveroneend

 alsopeakaseither andnegativeovertheotherend.

 polarity.



 +or‐ +‐



Figure7: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observingthedigital readout.Thevalueofthenumber

willbehighestwhenthelocatorisdirectlyover

averticaltargetorovertheendsofahorizontal

target.The“X”pattern,asshowninFigure8,isidealforpinpointingsmallobjects.Byusingthis

technique,a1‐1/4inchPKnailburiedupto8inchescanbepreciselylocated.



Figure8:“X”PatternprovidesPrecisionLocating



If you are looking for a corner marker and detect two more signals in the same general area,

raise the locatorseveralinches above the ground or reduce the sensitivity setting.Any signal

thatdisappearswhenthelocatorisheldhigherorwhenthe

sensitivityisdecreasedisprobably

comingfromashallowtarget.AsshowninFigure9,thesignalfromarustyboltorothersmall

itemdecreasesmuchfasterwithdistancethanthesignalfromalargertarget,suchasa18‐inch

lengthof3/4rebarthatcanbelocated

atdepthsupto7feet.

- 8 -

+ or -

Figure9:RaisingtheLocator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thiscanbemistakenfortheactualmarker.



The heavy line in Figure 10 represents the

increase and decrease in the audio and digital

indications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, peak directly over the

marker, and then decrease at point C.From C to

 D, the signals increase and decrease again.

Therefore,ifyou donotmovethe locatorcompletelyacrossthemarker,youmayassumethat

theweakerindicationoneithersideofthemarkerisitslocation.



 AudioSignal



B C

 A 0 0 D

 +or‐ +or‐ +or‐



 IRONPIPE



Figure10:SignalPatternfromaStronglyMagnetizedMarker

IRONPIPE

+or‐

- 9 -

The two weaker indications on both sides of the actual marker occur because the locator is

extremelysensitiveto themagneticfieldcomponentsparalleltoitslongaxis.AtpointBandC,

thefieldisperpendiculartothelocatorsonopeakaudioordigitalindicationsareproduced.



When

PlacingStakes,CorrectOrientationisImportant



Forcheckingpurposes,theorientationofthepinrelative

tothelocatorisshowninFigure 11.Checkthepin with

one orientation.Then ro tate the pin 180°.The

orientationthatgives thelargest reading isthe onethat

should be used.This reading

will be positive in the

Northern Hemisphere and negative in the Southern

Hemisphere(Australia,NewZealand,etc.)



An iron pin has two typesof magnetization.One is the

magnetizationinducedbytheEarth’smagneticfield.The

induced magnetization is always downward in the

Northern Magnetic Hemisphere and produces a positive

output

 no matter which end of the stake is driven into

the ground.The other type of field is the permanent

magnetization that is fixed to the pin.For maximum

detection,thestakeshouldbedrivenintothegroundso

that the permanent magnetization is in the same

directionasthe

inducedmagnetization.



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8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15feetdeep.



 Figure12:LocatingManholeCovers Figure13:LocatingWaterWellCasings

Figure11: CheckingaStake’s

Orientation

- 10 -

TheGA‐72Cdcanbeusedtopreciselylocatethemetalhandlesorreinforcingbarsonseptictank

coversatdepthsupto4feet.

+ or - AUDIO SIGNAL + or -

Figure14:SignalPatternsProvidedbySepticTankCovers



LocatingObjectsunderSnoworWaterandTracingBarbedWire



Thelocatorcanbeusedinsnoworinfloodedareas‐justkeeptheelectronicunitoutofthe

snoworwater.

Figure15:LocatingObjectsunderSnoworWater



- 11 -

Figure17: Searchinginthe

VicinityofaChainLinkFence

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).



Examinetreesforbenchmarksandbitsofembeddedbarbedwire.Thenholdthelocator

paralleltothedirectionofthewire.

Figure16:TracingBarbedWirefromOldFenceLines



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 17, position the locator

horizontally with its long

 axis perpendicular to

thefence.Thisensuresthattheuppersensoris

keptawayfromthe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18)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.

- 12 -

SIGNAL NULL

WITH LOCATOR

+ AS SHOWN

1-5/8

Figure18:PlacementofLocator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areeasilylocatedatdepthsof6feetormore.



Figure19:Locating

ValveBoxesandCasings



LocatingCast‐IronPipes



AsillustratedinFigure20,cast‐ironpipesproducethestrongestmagneticsignalsattheirjoints.



+or‐ +or‐



 1to1‐1/2Feet



Figure20:SignalPatternsProvidedbyCast‐IronPipes

- 13 -

Theinitialsearchshouldbeperformedasfollows:



1. SettheSensitivitycontrolformaximum(XHindication).

2. Holdthelocatorverticallyandapproximately1to1‐1/2feetabovethesurface.

3. Walk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upto8feet.



LocatingSteelDrums



As shown in Figure 21, the

 GA‐72Cd’s signal pattern will vary depending on the vertical or

horizontalorientationofthedrumandhowdeepitisburied.A55gallondrumcanbelocated

atdepthsupto8feet.



 SIGNALPATTERNFORDRUMSBURIED

 APPROXIMATELY4TO8FEET

 +OR‐



 SIGNALPATTERNFORDRUMSBURIEDAPPROXIMATELY4FEETORLESS

 +OR‐ +OR‐ +OR‐ +OR‐



Figure21:SignalPatternsProvidedbySteelDrums



LocatingOrdnanceandWeapons



The versatile, lightweight, cost‐effective GA‐72Cd is also

designed to aid EOD technicians and law enforcement

officersduringareasearchoperations.



Figure 22: Basic Signal Patterns from Vertical and

HorizontalTargetsHelptoDetermineTargetOrientation



+or‐ + ‐

- 14 -



Figure23:A175mmProjectilecanbelocatedupto4feetdeep.



Figure24:An81mmMortarcanbelocatedupto12inchesdeep.



Figure 25:MK81 Low Drag Bombs can be located up to 7

feetdeep.



Figure 26: A hunting knife under

water can be

locatedinupto16inchesofsilt.



Figure 27:A discarded hand gun can be located up to 12

inchesdeep.



- 15 -

AdditionalApplications



1. ThemilitaryandmanylocalandstatepolicedepartmentsusetheGA‐72Cdtodetectburied

ordnanceanddiscardedweapons.



2. Peopledrillinginanareawherehazardousmaterials mightbeencounteredshouldusethe

GA‐72Cdtosearchtheareapriortodrilling.



OtherNotes



1. Aburblingsoundindicatesthepresenceofanenergizedpowerline.Thiswillnotinfluence

themeterindicationunlessassociatedwithamagneticstructure.



2. The instrument will not respond to non‐ferrous metals such as gold, silver, copper, brass

andaluminum.



- 16 -

DATA LOGGER OUTPUT



Theheadsetjackalsoprovidesananalogoutputsignalforinputtoadatalogger.This+/‐4volt

signalvariesinproportiontosignalstrengthandisaccessiblebywiringastandardstereoplug.



 Gnd Tone

 DCOut

 (+/‐4VFS)



Figure28:StereoPlug

ConnectionsforAnalogOutputSignal



- 17 -

MAINTENANCE



The GA‐72Cd is designed and built to give trouble‐free operatio n.Normally, maintenance is

limitedtotheoccasionalreplacementofthebatteries.Intheeventa malfunctiondoes occur,

refertotheTroubleshootingGuideonpage18.



ReplacementofBatteries



TheGA‐72Cdispoweredbytwo9‐Volt

alkalinebatteries.Accessto thebatteriesisobtainedby

looseningthefourcaptivescrewsandremovingtheelectronicscover(asshowninFigure29).



It is recommended that you purchase spare batteries for this unit.When you use the spare

batteries, replace them as soon as possible so that you

will never be without batteries in the

field.



Figure29:ExplodedViewoftheElectronicUnitCover



- 18 -

TroubleshootingGuide



Symptoms PossibleCause HowtoCheck HowtoFix

Dead DeadBatteries



Batteriesnotmaking

contact



Batteryleakage

Replace



Checkforcontact

corrosion



Remove

‐‐‐‐‐‐‐‐



Cleancontacts



Returnunittofactory



Intermittent Batteriesnotmaking

goodcontact



Checkforcorrosion Cleancontacts

Uncontrollable

screaming

Weakbatteries



Replace ‐‐‐‐‐‐‐‐



SERVICE INFORMATION



If your locator needs service, please return it to the factory with the following  information:

Name, Address, Telephone and Fax Numbers, Email Address, Where Purchased, Date of

Purchase, and Description of Trouble(s).An estimate will be provided prior to service work

beingdone.Seeshippinginformationbelow:



FORSERVICEORREPAIR

Pleaseshiplocator(initscase)to:



SchonstedtInstrumentCompany

100EdmondRoad

Kearneysville,WV25430



- 19 -

SPECIFICATIONS

(Specificationssubjecttochangewithoutnotice)



InputPower:..............................Suppliedbytwoalkaline9‐Vbatteries**



BatteryLife:...............................40Hours(intermittentusage)



Output:



 Audio

OutputOption...........Signalincreasesordecreasesinvolume

Switchat“A” withgradient‐fieldintensity



OutputOption...........Signalincreasesordecreasesinfrequency

Switchat“B” withgradient‐fieldintensity



 Visual...............................Digitalreadoutexpandingbargraphs

 indicatepolarity(positiveornegative)and

 relativestrengthofthemagneticfield



BatteryCheck:...........................BATT4‐segmentLCD



Weight:......................................Approximately2.5lbs.(1.14kg)



OperatingTemperature:...........‐13°to140°F(‐25°to60°C)



OverallLength:..........................34.5in.(87.6cm)



WaterproofLength:...................21in.(53.3cm)



NominalSensorSpacing:...........14in.(35.6cm)



Construction:.............................Rugged,allsolidstate



**UnitspriortoSN:339698itisrecommendedtouseLithiumbatteries.UsingAlkalinebatteries

in these units will produce a magnetic field that will impact performance of the locator

(especiallywhensettotheHorXHsensitivityrange).



Thisdevicecomplieswithpart15oftheFCCRules.Operationissubjectto

thefollowingtwoconditions:(1)thisdevicemaynotcauseharmful

interference,and(2)thisdevicemustacceptanyinterferencereceived,

includinginterferencethatmaycauseundesiredoperation.



ApplicationofCouncilDirective(s):

2004/108/EC

Standard(s)towhichConformityisDeclared:

EN61000‐6‐1:2001,EN61000‐4‐2,EN61000‐4‐3,EN61000‐6‐3:2004,

EN55022:1998withAmendmentA 1:2000(CISPR‐22)



- 20 -

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 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 a

description 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coverproduct

that has been subject to inundation by fire,water or other liquid intrusion, or units that have

beendamagedorcompromisedduetorepair,alteration

ormodificationby anyoneotherthan

an authorized repair representative.Prior to a repair being performed by Schonstedt, a cost

estimate will be submitted and no work will be completed until authorized by the customer.

Batteries are specifically excluded under the warranty and should be addressed to the

manufacturerof

batteriesinquestion.



Schonstedt shall not be liable for any injury to persons or property or for any otherspecialor

consequentialdamagessustainedorexpensesincurredbyreason oftheuseofanySchonstedt

product.



*ForMilitary& EODapplications,thewarrantyis1year.

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Schonstedt Instrument GA-72Cd User manual

Brand: Schonstedt Instrument

Model: GA-72Cd

Category: Measuring, testing & control

Type: User manual

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Schonstedt Instrument GA-72Cd User manual

Schonstedt Instrument GA-72Cd User manual

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