Metal Samples MS2500L User manual

MS2500L Transmitter
Operator’s Manual
Metal Samples Company
A Division of Alabama Specialty Products, Inc.
152 Metal Samples Rd., Munford, AL 36268 Phone: [phone] Fax: [phone]
E-mail: [email protected] Internet: www.metalsamples.com

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TableofContents
I. Introduction ....................................................................................................................... 1
A. GeneralDescription ..................................................................................................... 1
B. PrincipleofOperation.................................................................................................. 2
C. ModesofOperation .................................................................................................... 3
D. Specifications .............................................................................................................. 4
E. Summary ..................................................................................................................... 5
II. InstallationProcedures ....................................................................................................... 6
A. MS2500LTransmitterMounting .................................................................................. 6
B. MS2510Receiver Installation ...................................................................................... 6
III. Operation ....................................................................................................................... 7
A. CycleTimePredetermination ....................................................................................... 7
IV. Accessories ....................................................................................................................... 8
A. MS2510Receiver/Power Supply ................................................................................ 8
B. Probesand Electrodes................................................................................................. 9
C. ElectrodesNormallyCarriedin Stock .......................................................................... 10
D. ProbePlacement ......................................................................................................... 11
E. ProbeInstallation......................................................................................................... 11
F. PAIRTM ProbeAssembly ............................................................................................. 12
V. CircuitDescription ............................................................................................................. 14
A. Introduction................................................................................................................. 14
B. LPRMeasurementTechnique ...................................................................................... 15
C. BasicStructure ............................................................................................................ 16
D. CircuitDescription....................................................................................................... 17
E. OperationModes ........................................................................................................ 20
VI. Calibration Procedure ........................................................................................................ 21
A. Disassembly ................................................................................................................ 21
B. EquipmentNeeded...................................................................................................... 21
C. ApplyingPower .......................................................................................................... 21
D. FrequencyCalibration ................................................................................................. 21
E. ZeroingAdjustments .................................................................................................... 22
F. CurrentSpanAdjustment ............................................................................................ 22
G. Disconnection .............................................................................................................. 22

VII. InstrumentTestingandRepair ........................................................................................... 23
A. RecommendedTestEquipment .............................................................................. 23
B. BoardRemoval ..................................................................................................... 23
C. ElectrostaticShieldRemoval .................................................................................. 23
D. VisualInspection ................................................................................................... 24
E. ElectricalTesting ................................................................................................... 24
VIII. CurrentLoopOperation andTesting ............................................................................... 28
A. RecommendedTestEquipment .............................................................................. 28
B. InstrumentandLoopVerification ............................................................................ 28
C. ProbeElementTesting ........................................................................................... 28
D. CurrentLoopIsolationTesting ............................................................................... 29
AppendixA:Drawings.............................................................................................................30
AssemblyDrawings..........................................................................................................31
InstallationDrawing ..........................................................................................................36
AppendixB:PartsList .............................................................................................................37
AppendixC: Effectsof ProcessVariables .................................................................................38
Temperature.....................................................................................................................38
pH 54..............................................................................................................................38
OxygenConcentration......................................................................................................38
FluidVelocity ...................................................................................................................38
SuspendedSolids.............................................................................................................39
ElectrodePotentials..........................................................................................................41
CommonCorrosiveAgents ..............................................................................................43
AppendixD:WarrantyInformation...........................................................................................44
AppendixE:MaintenanceandRepairInstructions ....................................................................45

1
I. Introduction
A. General Description
TheMS2500L corrosionratetransmitter isatwo-wire, 4-20mAcurrentloop transmitterforcorrosion
measurementsusingthethree-electrode,linearpolarizationtechnique(LPR).Functionally,theMS2500L
transmitteroperatesunder thesame principlesas theautomaticLPRinstrumentsoffered byMetal
Sampleswith theexception ofits low-powercurrentloop operation.
Figure1. MS2500L

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TheMS2500Ltransmitterishousedinanexplosion-proofenclosurewiththefollowingratings:
HousingRatings:
ClassI Groups B,C,D
ClassII Groups E,F,G
ClassIII NEMA 4X
FMApproved CSAApproved
TheMS2500L is equippedwith10 feet oftransmitter-to-probe cable and usesthe standard five-pin
environmentalconnectorfoundonallofourexistingLPRequipment.Thislight-armorcable passesinto
thehousingthroughanexplosion-proofcablegland.
Locatedinsidethe housingis anelectronics packageconsisting oftwo printedcircuit cards,the mount-
ingbracket forthe circuitcards,and allthe necessarytermination points forthe cableand current loop
connections.
Theterminationpointsontheprinted circuitcardsare constructedusingremovable terminalblocks.This
providesa permanentscrew type connectionwhich canbreak-away from theprinted circuitcardsfor
theireasyremoval.
Theprintedcircuit cardsrest insliderailswithinthe mountingbracket. Oncetheterminalblocksare
detachedfrom theprinted circuitcards, thecircuit cardsslideout ofthe instrumentfor easyrepair,
calibration,orreplacement.
B. Principle of Operation
TheMS2500L transmitter readsandstores the potentialdifference between a referenceelectrode and a
testelectrode. Itthen appliesa currentthrough anauxiliaryelectrode andthe testelectrode untilthe
potentialmeasurementbetween thetest andthe referenceelectrodes changesby10millivolts.The
instrumentthenallowsthiscurrenttosettlefor apredetermined lengthof time(polarization cycle), after
which,it samplesthis currentand updatesthe currentloopoutputusingthe conversionfactor of5.5 µA
per MPY.
Note:The surface area of the electrode has been adjusted where 5.5 µAconverts to 1 MPY.
Thepolarizingcurrent isthen turnedoff andthecellisallowed torelax forthe samelength oftimeasthe
polarizationcycle.

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CycleTimeAdjustment
TheMS2500Luses adigital timingcircuitwhichcanbe adjustedusing three10-position rotaryswitches
(Figure2).Thefirstswitchrepresents tensof minutes,the secondswitch representsminutes, andthe
thirdswitchrepresents tenthsofminutes. Thisallowsuser-selectabletimecycles from00.1minutes to
99.9minutesin00.1minuteincrements.Theswitches arelocated inthe upperright handcorner.
C. Modes of Operation
Anadditionalfeature thatis incorporatedinto theMS2500Ltransmitteristhe abilityto monitorand
transmitthecorrosion potentialof thecell.This aswitch selectablefunctionwherethe4-20mA current
looprepresents acorrosion potentialof 1V positiveor 250mV negativefullscale.
Ineither mode, LPRorOFFSET,the user canselect two differentmodesofcurrent loop response.
Thefirst mode isthenormal operation mode orSAMPLEmode. Thismode is as theone described
earlierwherethe currentloopinformationisupdated uponthecompletionofa measurementcycle.This
isthelogicalchoiceofoperation whentakingLPRmeasurementswherethecurrentloopinformation
constantlyrepresents thecorrosionrate inmilsper year.Thismode of operationcan also beused in
conjunctionwithelectrode potentialmeasurements wherethe corrosionpotentialcanbesampled and
thecurrent loopupdated on intervalsas setby the cycletime adjustment.
Thesecond mode of operationisthe TRACKmode.Inthis mode, the currentloop output is updated
every1.5 seconds.When takingcorrosion potentialmeasurements, thisprovides theuserwithacurrent
loopoutput thatconstantly tracksthecell corrosionpotential. For LPRmeasurements,thecurrent loop
willreflectthe cellresponse totheapplied current.This providesanexcellentmethodfor selectingthe
cycletimefor thenormal modeof operation.
Figure3. Front Board
Figure2. Back Board

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D. Specifications
Model
MS2500L- Loop-Powered LPRTransmitter (Ordering # IN2500L)
Physical Data
InstrumentWeight: 5.02 lb. (2.28 Kg)
TotalWeightw/Accessories: 7.08 lb. (3.21 Kg)
InstrumentDimensions: 5.81"Hx 4.5"Wx 4.81"D (14.76cm x 11.43cm x 12.22cm)
CaseSpecifications: ExplosionProof (FM, CSA, CENELEC, UL)
Class I, Groups B, C, D, Class II, Groups E, F, G, Class III,
CENELEC: EexdIIC NEMA4X, 7BCD, 9EFG
MountingSpecifications: 0.728"Hx 1.756"W (1.85cm x 4.46cm)BoltPattern with 1/4-20
Tapped Mounting Holes, or MayBeMounted on a 1/2" to 2"
(1.27cmto 5.08cm) PipeUsing Supplied Hardware
OperatingTemperature: 32° to 158°F (0° to 70°C)
StorageTemperature: 32° to 158°F (0° to 70°C)
PerformanceData
MeasurementType: 3-ElectrodeLPR,Potential
Range: 3-Electrode:0-100mpy Potential:± 1V
CycleTime: 0.1to 99.9minutes
Electrical Data
PowerRequirements: 11 to 35 VDC
MaximumProbeCableDistance: 10 ft (3.05 m)
OutputSpecifications: 4-20mACurrent Loop Output
Special Features
• Switchselectablemeasurementtypeandcycletime
• Loop powered
Accessory Items
10'Probe Cable (attached), Meter Prover, MountingHardware,Operation Manual

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E. Summary
TheMS2500Ltransmittermoveson-line corrosionmonitoringintothe realmofconventionalplant
practiceby placing the D.C.- powered transmittercloseto the corrosion rate probe (thesensor)and
usingthetwo-wiresignal loopto provideboth thepower tothe transmitterand theproportionalsignal
correspondingto the data.
UserSelectableOperation
Switcheson thetransmitter’scircuit boardallow the userto selectnecessaryparameters suchas:
•OperationMode:Trackor Sample
•CycleTime:.1 - 99.9 minutes
•TransmitterDataType: CorrosionRate (MPY) or Electrode Potential(mV)
LowCost
Sincethetransmitter isof thetwo-wire type,theinstalledcostof aninstallation isfar lessthan ifthe
analyzeris locatedin thecontrol roomand signalcablesarerunfrom thesensor tothe analyzer.
Safe
Thetransmitteritselfis housedinacompactexplosion-proofhousing.
StandardizedOutput
Sincethe4-20mAdatasignal fromthetransmitteristhemostcommon inindustrial usetoday,the
displayof thecorrosion ratedata issimplified.The datamaybe displayedon asuitable recorder, digital
voltmeteroron theoptionalMS2510 digitaldisplayunitwhichwill displayloopcurrent, corrosionrate
(MPY),or electrodepotential (mV). TheMS2510 also hasan auxiliarypowersupply forpowering the
transmitterand acurrentloop outputforpassing thedataon toanotherreading device.
PAIRTM probes (3-electrode, Linear Polarization type) can be used as sensors for the MS2500L
withoutmodification.

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II. Installation Procedures
A. MS2500L Transmitter Mounting
WhenmountingtheMS2500Lchoosealocation thatis freefrom vibration.The mountingbracket (U-
bolts)can accept a pipe that isnolarger than 2.5 inches.
Alwaysremovepowertotheinstrumentwhenmounting;especiallywhenmountingitin ahazardous
area.
(SeeDrawing No.8102 in AppendixA forpreferred hardware mountingscheme.)
B. MS2510 Receiver Installation
TheMS2500Ltransmittercan beused in conjunctionwiththe MS2510 receiver.(See Drawing No.
8101inAppendixAfor connecting thesetwo instruments together.See Section IVfordescription and
specificationsoftheMS2510.)
FrontPanel
Two of the three positionsonthe front panel of the MS2510 are usedwiththe MS2500L. One is the
loopcurrentin milliampsandtheother(far right)iscorrosionratein milsperyear.
Back Panel
Theback panel’s10-position rotary switches must be set to 999 when operatedintheCorrosionRate
Mode.In CurrentLoopModethe switch positionsdonot matter.
WireConnections
Oncethe MS2500Lis installed, connectionsare made byconnecting the redwire (+) comingout ofthe
MS2500Lto the (+) side of terminals on back of the MS2510 receiver labeled - LOOP+. Connect
the black wire (-) to the (-) side under - LOOP +.

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III. Operation
A. Cycle Time Predetermination
Thefollowingprocedureassumesboththemechanicalandelectricalinstallationoftheinstrument.This
procedurealsorequiresthat someform ofdevice isavailable formonitoring theloop(ie., DVM,chart
recorder, etc).
1. Connect theinstrumentcable totheprobe.
2. Set the sample timeadjustswitches on the MS2500L to 999.
3. Set the operation switchestoLPRand TRACKmode.
4. Power up theloopand observe the loop current (usingaammeter,recorder, etc).The
currentreadingwill changeeverytwoseconds.These readingswillthen beginto settle.
Dependingupon theconditions, thismaytake from30 secondsto 30 minutes.Record this
timeinterval.
Figure4.SettleTime
5. Set thesampletimeadjustswitches tothistime interval.
6. Set the operation switchestoLPRand SAMPLE.
7. Cycle the loop power on and off. (BreakLoop)
8. The instrumentis nowin therun modeand willupdate thecurrent loopoutput onceevery
twosampletimeintervals.

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IV. Accessories
A. MS2510 Receiver/Power Supply
Whenoperated together,the MS2510 receiver and MS2500Ltransmitterprovidethe corrosion
investigatorwitha low-cost,4-20mAcorrosion monitoringsystem.Datareceivedfrom thetransmitteris
displayedonthe receiver’s frontpanel, athree digitL.E.D.Thethree-positionfunctionswitch,located
atthe center ofthereceiver’sfront panel,permitsthe data to bedisplayed in one oftwo formats,
dependingon switchposition: milliampsand corrosionrate (MPY). Locatedat theback ofthe receiver
are4-20mAand 10Voutput terminalsfor connection ofthe receiver toa customer-suppliedcomputer,
datalogger, or recorder;connectionterminals for the MS2500L; and anACpower cord connector.
General Specifications - MS2510
Display: 3-digitL.E.D.displaytogive:
a)Loop Current(in mA)
b) Probe Reading (0-100 MPY)
Dimensions: Length: 5.25"
Width:2.0"
Height:6.6"
Required
InstallationSpace: 4.3" x2"
Weight: 3lbs.
ElectricalSpecifications- MS2510
PowerRequirements: 120/240V AC 50/60 Hz @ ½ Amp
Outputs: 24V DC - 4 to 20 mA current loop drive
4-20mA - isolated output to CPU, etc.
0-10V- isolated output to chart recorder

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B. Probes and Electrodes
ThePAIRTM probes usedinconjunctionwithMetal Samplescorrosion rateinstruments arean essential
componentof acorrosion ratemeasuringsystem. Forthis reason,thecomposition ofthe electrodes
installedon theprobe must bematched as nearlyas possible tothe composition ofthe componentsof
theprocessing systemin whichthe probeand electrodesareinstalled. Inaddition, theplacement ofthe
probeisextremely importantin obtainingaccurate corrosionratereadings.Basically,aprobeissimplya
meansof mountingthe threeelectrodes whichare necessaryto makethecorrosionratemeasurement
andprovidesa meansofelectrically connectingthe electrodes,thecomposition ofwhichisdetermined
bythecustomer.
Theprobes aregenerally classifiedinto twotypes:laboratory probesand industrialprobes. Allprobes
aresuppliedwithMIL environmentalelectricalconnectorsunlessotherwisespecified.For further
informationonprobesandelectrodescontact:
MetalSamples
P.O. Box 8
Munford,AL 36268
Phone: [phone]
Fax: [phone]
E-mail:[email protected]
Internet:www.metalsamples.com

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C. Electrodes Normally Carried in Stock
EL-600 Lazaran1ReferenceElectrode withone VITON2Gasket
EL-601 Aluminum,Alloy6061(standard)
EL-610 Copper (99.0% Pure)
EL-611 Brass (85-15)
EL-612 AdmiraltyMetal
EL-613 Copper-Nickel
EL-614 Aluminum/Bronze(92Cu-8Al)
EL-615 Copper-Nickel (70-30)
EL-620 ColdRolled Mild Steel(1018)0.250" Dia.
EL-621 ColdRolled Mild Steel(1018)0.375" Dia.
EL-630 304Stainless Steel
EL-631 316Stainless Steel
EL-632 410Stainless Steel
EL-633 430Stainless Steel
EL-634 304Low Carbon Stainless Steel
EL-635 316Low Carbon Stainless Steel
EL-640 Hastelloy3B
EL-641 HastelloyC
EL-643 HatelloyN
EL-651 Nickel200
EL-652 Inconel4600
EL-653 Inconel625
EL-654 Incolloy4800
EL-655 Incolloy825
EL-657 Monel4
EL-658 Alloy20 Cb5
EL-660 Zinc
EL-671 Titanium
EL-672 Tantalum
EL-673 Zirconium
EL-687 Aluminum/Brass
EL-681 ReplaceableElectrode AssemblyforPR-556-E Flush MountedProbe
1 Registered trademark of Beckman Instruments, Inc.
2Registered trademark of DuPont.
3Registered trademark of Stellite Division, Cabot Corp.
4Registered trademark of Huntington Alloys Inc.
5Registered trademark of Carpenter Technology.

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Properprobelocation isthe firstand oneof themost importantconsiderations inobtainingpertinent
datawith thecorrosion rate instrument.Any systemcanbe expectedto have corrosionoccurring at
severalratesasa functionof locationwithin thesystem. Thedifferent ratesmay bedue tochangesof
temperature,changesinvelocity,impingementeffects,differencesofmetallurgy,variationsincharacter
offluidstream,etc.Itis thereforeunlikely thata singleprobe locationwill beable toproduce quantita-
tivecorrosion ratedata forthe overallsystem. Eachprobe does,however,providevaluable information
byreadingthecorrosionattheparticularlocation,andbyindicatingthegeneralrange ofoverall corro-
sionbyfollowing changesincorrosion ratescausedby adjustmentsininhibitors,oxygenlevel orprocess
variables.
Thechangeincorrosionrateofasystemduetoalteringavariableshouldbeindirectratioforallpartseven
thoughthe absoluterates arewidely different. Forinstance, ifthe additionofan inhibitorwill reducethe
instrument’sreadingby90percent,allnormalsurfacesofthesame metalcontactedbytheinhibitorshould
havetheircorrosionratessimilarlyreduced.Usually,aprobelocationisselectedtoreadonthehighsideof
asystem’s average ratein order to accentuatechanges.
It should be emphasized that a corrosion rate reading is the actual corrosion rate taking place on the
surfaceof theTest electrodeat thetimeof measurement.
Thecondition of theprobe’sTest electrode surfacedueto past service,as well ascurrentprocess condi-
tions,mayhave animportantbearingonthe readings.
Thecorrosionengineer ischallengedto adapttheabovetohis situationandinterpret theresultsInlightof
thelocationandoperational factorsinvolved.
E. Probe Installation
Probeinstallationsshouldgenerallybeselectedonthefollowingbasis:
1. Locate the probeas close as possibleto the warmest sectionof the system. Ifvaporization is
experiencedinthe process,the probeshould beinstalledimmediatelyaftercondensation.
2. If thefluid isnormally flowing,it isrecommended thatthe probebe insertedin sucha wayas to
experienceapproximatepipe wallvelocity.Theprobeshouldnotbeinstalledin astagnant sectionof
line.Someturbulence atan elbowor teemay resultin slightlyhigh, butacceptable, corrosionrate
readings.
D. Probe Placement

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3. Direct fluidimpingement onthe probe’s electrodes(at avery highvelocity ofabout 10-feet-per-
secondorso),shouldbeavoided asthis usuallyresults inabnormally highcorrosion ratesaggra-
vatedby erosion.
4. The probeshould notbeinstalled ina positionwhere solidsare likelytocollect.Solidscan buildup
onthe probe base andelectrically short out theelectrodes.
5. Any surfaceareain contact withahydrocarbon phase orgasphase will notbecorroding. There-
fore,representative maximumcorrosion ratesare obtainedwhen thetotalTestelectrodesurface is
inwateror electrolyte.
6. A bypasslooparound a sectionof the mainpiping may beconsidered.Probe inspection and
electrodereplacement canbe madewithout systemshutdown.Effects ofvelocity canbe checked
bythrottlingofbypassvalves.
Theaboveisfurnishedasageneralguideline.Theexistingphysicalfacilitiesofmostsystemswilldictate
theprobe location.If thisturnsout tobe inconflict with theideal considerations,the probe shouldbe
installedkeepinginmindthe problemsthatmayarise.
F. PAIRTM Probe Assembly
Allprobes with replaceable electrodesareshipped with the electrodes andgaskets in a separate packet
ifthe electrodes arepurchasedwith the probes.
Whenready to install,openthe packet andplace one of thegaskets on each ofthe three mounting pins.
PinA is connectedtothe Referenceelectrode, PinsBand Dare connected tothe Test electrodeand Pin
CisconnectedtotheAuxiliary electrode.
Figure5.ElectrodeMountingConfigurations

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Theelectrodes should notbe handled with baresweaty or oilyhands.If possible, pickup the electrodes
witha paper towelor clean clothand thread ontoeachof thethreemounting pins. Theelectrodes
shouldbefirmly handtightened inplace sufficientlyto deformthe gasket.A oneinchpieceofplastic
tubingslippedover anelectrode isaneffective meansof tighteningitontheprobe withoutsoil or
damage. Do not force with pliers or in a vise, as this will mark the surfaces. Do not use thread
lubricant.
Themildsteel electrodeshave beengivenasurfacepreparation topermit fastestpossible equilibriumto
thesystem.Anyforeignmaterialsuchasgrease,oilorsweatwilldelay obtaininguniformreadings.
Shouldachangeinlocationorenvironmentalservice ofmild steelelectrodes bedesired, theelectrodes
needtoberemoved,scrubbedwithscouring powder and water, and then placed in a beaker of 5-10
percenthydrochloricacid(uninhibited)until thesurfaces areuniformly coveredwith alayerofhydro-
gengasbubbles.They shouldberinsed thoroughlyinclean waterbeforereinstalling.Thisactionis
usuallysufficienttopreventeffectsofpreviousserviceseriouslyinterferingwiththenewapplication.

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V. Circuit Description
A. Introduction
TheMS2500LisaLinearPolarizationResistance(LPR)typecorrosionmonitoringinstrumentthat
translatescorrosionrates obtainedfrom polarizationtechniquesintoa4-20ma currentwhich isthen
transmittedthrougha two-wiretwisted cable.
ThisinstrumentalsoincorporatestheabilitytomonitorandtransmittheCorrosionPotential, obtained
fromLPR probesusing a referenceelectrode. The powerfor the instrumentis suppliedonthe sametwo
wiresthatreturn thecorrosion ratesignal.Therefore,to powerits internalcircuitry,theinstrument can
usenomore thanthe fourmilliamp, livezero, currentsupplied onthe loop.This 4-20mAtype ofmoni-
toringinstrumentationhasbecomeastandardintheprocessmonitoringindustry.The4and20milliamp
valuesare usedfor severalreasons:
1. A power supply voltageof25volts or more can be supplied to overcome long cabledropsor to
fulfillpowerrequirementsfortheinstrumentation.
2. The 4milliamp livezero notonly providescurrenttopowerthe instrument,but alsoprovides a
methodtodetermine loopfailure.If thezerooutputpointof theinstrumentwas atzeromilliamps,
therewould benoway to differentiatebetween a zerooutput or afailurein theloop.
3. The transmissionof alowimpedance signal,(such asacurrent), ratherthan ahighimpedance signal,
(suchasa voltage),setsup atransmission techniquethatis muchmoreimpervious.Generally,noises
inducedonto signalcables areof very highimpedances. Itwould takeavery largeexternal forceto
inducea noise signalontothe loopata current of4mA or more.Again,if a truezero point were
used,it mightbepossible to inducea noise erroraround the zerocurrentlevel. However,the use of
the4mAlivezero precludesthispossibility.

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B. LPR Measurement Technique
TheLPRtechnique isanearinstantaneousmethod fordeterminationofcorrosionrates usingPAIRTM
probesor similar probes.It is a simpleprocess which incorporatesseveralsteps.
1. The potentialdifferencebetween the testand the referenceelectrode is sampledand recorded.
2. Acurrentisforcedbetween theauxiliaryand testelectrodesuntil theoriginalpotential differenceis
changedby10millivolts.
3. This polarizationcurrent isallowedtosettlefor auserspecifiedduration.
4. The currentisthen sampled anda conversion factoris used tocalculatethe MPY value.5.5 µA/
MPY.
5. The polarizationcurrent isrelaxedfor thesame durationafter which,theprocess canthen be
repeated.
TheMS2500L instrumentincorporates the circuitrynecessary to performthe above stepsas wellasthe
abilitytomonitor andtransmit thepotential differencebetween thereference andtestelectrodes.
Followingtheabovedescription,thecircuitryisdividedintoseveralsections:
•Potentialmeasurementandrecording.
•Polarizationreferenceandcurrentcontrol.
•Clockandtimingcircuits.
•Polarizationcurrentmeasurementandconversion.
Generalcircuitryrequiredfor theoperationof theinstrument.
•Powersupplies.
•Currentloopsensing andcontrol.
•Power on reset

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C. Basic Structure
Thecircuitry forthe MS2500Lis containedontwo circuitcards.
TheA1Boardcontainscircuitryfor:
•Corrosionpotentialmeasurement.
•Corrosionpotentialnullandhold.
•10millivoltprobepolarizationandreference.
•Polarizationcurrentcontrol,measurementand conversion.
TheA2Boardcontainscircuitryfor:
•Powersupplies.
•Clockandtimingcontrolcircuits.
•Power on reset.
•Currentloopsensing andcontrol.
•Outputsampleandhold.