Droplet CDP-2 User manual

Cloud Droplet Probe
(CDP-2)
Operator Manual
DOC-0343, Rev A
Includes Documentation on
Particle-by-Particle Feature
2400 Trade Centre Avenue
Longmont, CO 80301-5727 USA

DOC-0343 Rev A
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
II

2400 TRADE CENTRE AVENUE
LONGMONT, COLORADO, USA 80503
TEL: [phone]
FAX: [phone]
WWW.DROPLETMEASUREMENT.COM
All rights reserved. No part of this document shall be reproduced, stored in a retrieval system, or
transmitted by any means, electronic, mechanical, photocopying, recording, or otherwise, without
written permission from Droplet Measurement Technologies, LLC. Although every precaution has
been taken in the preparation of this document, Droplet Measurement Technologies, LLC. assumes
no responsibility for errors or omissions. Neither is any liability assumed for damages resulting from
the use of the information contained herein.
Information in this document is subject to change without prior notice in order to improve accuracy,
design, and function and does not represent a commitment on the part of the manufacturer.
Information furnished in this manual is believed to be accurate and reliable. However, no
responsibility is assumed for its use, or any infringements of patents or other rights of third parties,
which may result from its use.

TrademarkInformation
All Droplet Measurement Technologies, LLC. product names and the Droplet Measurement
Technologies logo are trademarks of Droplet Measurement Technologies, LLC.
All other brands and product names are trademarks or registered trademarks of their respective
owners.
Warranty
The seller warrants that the equipment supplied will be free from defects in material and workmanship
for a period of one year from the confirmed date of purchase of the original buyer. Service procedures
and repairs are warrantied for 90 days. The equipment owner will pay for shipping to DMT, while DMT
covers the return shipping expense.
Consumable components, such as tubing, filters, pump diaphragms, and Nafion humidifiers and
dehumidifiers are not covered by this warranty.


Manual, Cloud Droplet Probe (CDP-2)
DOC-0343 Rev A III
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
LaserSafetyInformation

TheCDPcontainsaclassIIIBlaser.AVOIDDIRECTEXPOSURETOTHEBEAM.Observelasersafety
precautionsandwearappropriatelasersafetyglasses.Avoidplacingreflectivematerialsinthebeam
thatcouldredirectthebeam,includingwatchbands,ringsortools.

STRICTOBSERVANCEOFTHEFOLLOWINGWARNINGLABELSISADVISED.

ThefollowinglabelislocatedontheCDP:



DOC-0343 Rev A
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
4
CONTENTS
1.0ProductDescription............................................................................................8
1.1Introduction...........................................................................................................................8
1.2GeneralSpecifications...........................................................................................................9
1.3ElectricalSpecifications.......................................................................................................10
1.4PhysicalSpecifications.........................................................................................................10
1.5OperatingLimits..................................................................................................................10
2.0ProbeSetup.......................................................................................................11
3.0TheoryofOperation..........................................................................................11
3.1PbPOption..........................................................................................................................13
3.2CDPDataAcquisitionFeatures............................................................................................13
4.0ParticleAnalysisandDisplaySystem(PADS)......................................................14
5.0DynamicThresholdFeature...............................................................................15
5.1DynamicThresholdforSizerSignal.....................................................................................15
5.2DynamicThresholdforQualifierSignal...............................................................................16
6.0InstrumentMaintenanceandTroubleshooting..................................................16
6.1TroubleshootingwithHousekeepingChannels...................................................................16
7.0Calibration.........................................................................................................18
7.1RequiredEquipment...........................................................................................................19
7.2Instructions..........................................................................................................................20
AppendixA:RevisionstoManual...................................................................................23
AppendixB:GlassBeadtoWaterDropletConversionTableforCDP‐2s..........................24
AppendixC:CDPAlignmentResponse............................................................................25
AppendixD:CommunicationsbetweenthePCandCDP..................................................30
CommunicationsParameters..........................................................................................................30
InitiatingCommunications..............................................................................................................32
CommunicationsCommands..........................................................................................................32
SETUPDATACommand...................................................................................................................32
DefinitionoftheDeclaredParameters...........................................................................................34
CDPResponsetoSETUPDATACommand.......................................................................................34

Manual, Cloud Droplet Probe (CDP-2)
DOC-0343, Rev A 5
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
SENDDATACommand.....................................................................................................................35
CDPResponsetotheSENDDATACommand..................................................................................35
DefinitionsoftheSendDataResponseparameters....................................................................37
ResponseDataPacketLengthandTransmissionRate................................................................38
CDPHousekeepingChannels........................................................................................................39
SENDPbPDATACommand..............................................................................................................40
CDPResponsetotheSENDPbPDATACommand...........................................................................40
ResponseDataPacketLengthandTransmissionRate................................................................41
DefinitionsoftheSENDPbPDATAResponseparameters...........................................................42
ChangingtheSerialInterfaceType..................................................................................................42
AppendixE:MountingConsiderations............................................................................43
AppendixF:DMTInstrumentLocator—OperatorGuide.................................................45
Purpose............................................................................................................................................45
Installation.......................................................................................................................................45
Operation.........................................................................................................................................45
AppendixG:CDP‐2DimensionalDrawing.......................................................................46
AppendixH:ThresholdTableforCDP‐2.........................................................................48
List of Figures 

Figure1:CloudDropletProbe...........................................................................................8
Figure2:CDPTheoryofOperation..................................................................................12
Figure3:CDPwithImportantComponentsLabeled........................................................13
Figure4:CDPData,Histogram,andParticleImages........................................................14
Figure5:IdentifyingaNoiseBand..................................................................................15
Figure6:DisplayofCalibrationTestResults.Notethedefinitepeakinthe12‐14µm
particlerange...........................................................................................................18
Figure7:CompressedGasCansor“Dusters”..................................................................19
Figure8:BottleofGlassBeads,DMTOP‐0591‐0020.......................................................19

DOC-0343 Rev A
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
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Figure9:GlassBeadDispenser,DMTAD‐0164................................................................20
Figure10:CleaningtheGlassBeadDispenser..................................................................20
Figure11:TappingtheBeadDispensertoDislodgeBeads...............................................21
Figure12:DispenserwithFilmofBeadsonBottom.........................................................21
Figure13:CDPCalibrationFixture...................................................................................22
Figure14:ReleasingGlassBeadsintotheCDP.NotethispictureisofaCDPattachedtoa
CCP;operationisthesameforstand‐aloneCDPs.....................................................22
Figure15:8‐mglassbeadsCDPaligned.........................................................................25
Figure16:8‐mglassbeadsCDPmoderatemisalignment...............................................26
Figure17:8‐mglassbeadsCDPseveremisalignment....................................................26
Figure18:20‐mglassbeadsCDPaligned.......................................................................27
Figure19:20‐mglassbeadsCDPmoderatemisalignment.............................................27
Figure20:20‐mglassbeadsCDPseveremisalignment.................................................28
Figure21:40‐mglassbeadsCDPaligned......................................................................28
Figure22:40‐mglassbeadsCDPmoderatemisalignment............................................29
Figure23:40‐mglassbeadsCDPseveremisalignment.................................................29
Figure24:20‐mglassbeadscalibrationoverload..........................................................30
Figure28:CDPMountingInformation.............................................................................43
Figure29:CDPElectronicsMounting...............................................................................44
Figure30:InstrumentLocator.........................................................................................46

Manual, Cloud Droplet Probe (CDP-2)
DOC-0343, Rev A 7
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
List of Tables


Table1:PC‐CDPCommunicationsParameters................................................................31
Table2:DataStructuresUsedinCDP‐HostComputerCommunications..........................31
Table3:SetupCommand–DataPacket..........................................................................33
Table4:CDPResponsetoSetupCommand–DataPacket..............................................35
Table5:SendDataCommand–DataPacket...................................................................35
Table6:CDPResponsetoSendDataCommand‐‐DataPacket.......................................37
Table7:ConversionEquationsforAnalog‐to‐DigitalHousekeepingChannels.................39
Table8:SendPbPDataCommand–DataPacket............................................................40
Table9:CDP‐PBPResponsetoSendPBPDataCommand–DataPacket.........................41


DOC-0343 Rev A
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
8
1.0 Product Description
1.1 Introduction
TheCloudDropletProbe(CDP)isdesignedtomeasureclouddropletsizedistributionfrom2µmto
50µm.TheCDPandanappropriatedatasystemcanalsocalculatevariousotherparameters
includingparticleconcentrations,effectivediameter(ED),MedianVolumeDiameter(MVD),and
LiquidWaterContent(LWC).
DropletMeasurementTechnologies(DMT)hasimplementedstate‐of‐the‐artelectronicsandoptics
thatofferflexibilitytotheCDPuserinavarietyofapplications.Theminiaturizedandstreamlined
housingallowsuseinavarietyofground‐basedorairborneapplications.
TheParticleAnalysisandDisplaySystem(PADS)offersagraphicaluserinterfaceatthehost
computer.PADSprovidescontrolofCDPmeasurementparameterswhilesimultaneouslydisplaying
real‐timeparticlesizedistributionsandderivedparameters.Allstandarddatainterfacesaredone
vialinedriversmeetingtheRS‐422electricalspecification,allowingcablelengthsofupto100
meters.
Figure1showstheCDP.FordetailsonspecificcomponentswithintheCDPhousing,seeFigure3.
TheCDPprobehousingcontainstheforward‐scatteropticalsystem,whichincludesalaserheating
circuit,photodetectors,andanalogsignal‐conditioning.Thesignalsaretransmittedviaarobust
differentialdriver/receiverinterfacetotheCDPElectronicsModule,orCDPE.There,thesignalsare
receivedandprocessed,particlepulsesaredigitizedandcategorized,eightdifferent
“housekeeping”parametersaretracked,andaserialdatastreamineitherRS‐422orRS‐232
standardformatissentontotheuser’sdatasystem.

Figure 1: Cloud Droplet Probe

Manual, Cloud Droplet Probe (CDP-2)
DOC-0343, Rev A 9
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
1.2 General Specifications
Measured Parameters: Single-particle light scattering
Derived Parameters:
Particle diameter
Particle number concentration
Liquid water content (LWC)
Effective diameter (ED)
Median volume diameter (MVD)
Measured Particle Size Range: 2 µm – 50 µm
Number Concentration Range: 0 – 2,000 cm3
Typical Sample Area: 0.24 mm²
Air Speed Range: 10 - 250 m/sec
Sampling Frequency: Selectable, 0.04 sec to 20 sec1
Refractive Index: non-absorbing, 1.332
Light Collection Angles: Optical design: 4 - 12
Optical performance: 1.7 - 14
Laser: 658 nm, up to 50 mW
Data System Interface: RS-232 or RS-422 serial interface
Calibration: Precision glass beads

1 Versions of the Particle Analysis and Display System (PADS) earlier than 3.5 assume a
sampling frequency of 1 sec / 1 Hz. As a result, this frequency is recommended if you are using
PADS 2.7 or earlier. CDP-PBPs are also limited by the baud rate; a sampling g rate of
faster than 2 Hz may compromise the data.
2 A refractive index of 1.33 for water is the industry standard. Contact DMT for support for
measuring particles with other refractive indexes.

DOC-0343 Rev A
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
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1.3 Electrical Specifications
System: 28VDC at 2A
Anti-Ice: 28VDC at 12A
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
1.4 Physical Specifications
Probe Weight:
1.37 kg / 3.0 lbs (standard version); a
lighthweight UAV version is also
available
Electronics Box and Header Cable
Weight: 0.82 kg / 1.8 lb
Probe Dimensions: 26.7 cm L x 17.5 cm W x 21.6 cm H
(10.5” L x 6.9” W x 8.5” H)
Electronics Box Dimensions: 17.8 cm L x 8.9 cm W x 5.1 cm H
(7.0” L x 3.5” H x 2.0” H)

1.5 Operating Limits

Temperature: -40 to +40 °C
Altitude: 0 - 50,000 feet
Humidity: 0 - 100%, non-condensing
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

Manual, Cloud Droplet Probe (CDP-2)
DOC-0343, Rev A 11
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
2.0 Probe Setup
ForCDPsthatareattachedtoCloudCombinationProbes,seetheProbeUnpackingandHandlingsection
intheCloudImagingProbeOperatorManual,DOC‐0028.
Stand‐aloneCDPsarriveinapaddedcarryingcase.Theinstrumentshouldbehandledcarefully;holdingit
bythestrutisbest.IntheeventthatCDPsneedtobeshippedbacktoDMT,repacktheCDPinitspadded
carryingcase.InstructionsforsettinguptheCDPareontheinsideofthefrontcover.
3.0 Theory of Operation
TheCDPusesalasertoilluminateparticlesandforward‐scattertheirlight.Thedetectedscattered
lightisthenusedtosizetheparticles.
Theintensityofthescatteredlightdependsuponthesize,composition,andshapeoftheparticle.
Foraccuratesizing,theCDPmustacceptandsizeonlyparticlesthatpassthroughauniformpower
regionofthelaserbeam.Thisregionofthelaseriscalledthedepthoffield.TheCDP“qualifies”
particlesthatfallwithinthedepthoffield,andtheinstrumentonlysizestheseparticles.
Asparticlespassthroughthelaserbeam,lightscattersinalldirections(Figure2).TheCDPcollects
forward‐scatteredphotonswithinaconethatis4to12fromthelaserbeam.(Photonswithinthe
0to4rangeareconsideredpartoftheunobstructedlaserbeamandaredivertedelsewheresoas
notburnoutthephotodetectors.)Thecollectedlightisthendirectedontoa50/50opticalbeam
splitterandfinallytoapairofphotodetectors.Thesetwodetectorsarereferredasthesizerand
thequalifier.Anopticalmaskfilterstheopticalsignalgoingtothequalifier,andonlysignalsfrom
particlesthatfallwithinthelaser’sdepthoffieldreachthequalifierinsignificantquantityand
focus.
Bothphotodetectorsthenconvertthephotonpulsesintoelectricalpulses.Thepulsefromthe
qualifieristhenmultipliedbytwo.Iftheresultingsignalexceedsthepulsefromthesizer,aDOF
flagissettotrue,indicatingtheparticleiswithinthedepthoffield.

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



Fi
g
ure
2
: CDP Theor
y
of O
p
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Figure3showswherethesecomponentsarelocatedontheactualCDP.


OncetheCDP’selectronicshaverecorded,amplified,andevaluatedtheparticlesignaltoseeifthe
particlefallswithinthedepthoffield,theanalogvoltagevalueisdigitized.Thepeakdigitalvalue,
whichcorrespondstotheparticle’ssize,isthencategorizedintooneof30bins.Thehistogram
resultingfromallparticlessizedduringthesampleintervalistransmittedtoanexternalcomputer
viaanRS‐232orRS‐422serialpacket.
3.1 PbP Option
AnoptionfortheCDPistheinclusionofParticle‐By‐Particleinformation.Thisinformationincludes
inter‐arrivaltimeandtheexactpulseheightwith12‐bitresolutionforthefirst256particlesevery
sampleinterval.
3.2 CDP Data Acquisition Features
TheCDPprovidesthefollowingdatainitsserialstreamoutput:
 Classificationofparticlesizesinhistogramform.

Figure 3: CDP with Important Components Labeled

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 Monitoringofmultiplehousekeepingvariables,e.g.totalparticles,averagetransittime,
lasercurrent,dumpspotmonitor,CDPinternaltemperature(“WingboardTemp”inthe
datapacket),orparticlesrejectedduetotheirtransittimeorDOF.
 OptionalPbPdataonupto256particlespersampleinterval.
Formoreinformationontheinstrument’soutput,seeAppendixD.
Theinstrumentalsofeaturesuser‐programmablesamplerates,numberofbins,andbinthresholds.
Therearezerodeadtimelosses.
4.0 Particle Analysis and Display System (PADS)
DMT’sParticleAnalysisandDisplaySystem(PADS)isaWindows‐based,LabVIEWsoftwarepackage
thatisthedefaultinterfacesystemfortheCDP.Itoffersattractivedisplayandanalysisfeatures,
anddataacquiredwithPADScanbestoredtoafileforlateranalysis.Theprogramalsostoresall
configurationinformationasafileheader,souserscaneasilydeterminethesystemsettingsatthe
timeofdataacquisition.
PADSautomaticallycalculatesvariablessuchasparticlenumberconcentrationandvolume
concentration,effectivediameter,andliquidwatercontent.Itcreatestime‐serieschartsofuser‐
specifiedvariablesanddisplaysahistogramofparticlecountsbysize.Anycomputerwithan
availableserialport,PADSsoftware,andaPADShardwarekeycanactasthedataacquisition
device.Figure4showsPADSdisplayingdataacquiredwiththeCDP.
Figure 4: CDP Data, Histogram, and Particle Images

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PADSisalsousedtoconfigurethesetupfortheCDP.Forinstance,theprogramallowsusersto
specifythetimeintervalatwhichtheproberelaysdatatothecomputer,thelocationsofthreshold
tablesusedinparticlesizing,andsoon.SeethePADSOperatorManual(DOC‐0116),thePADSCDP
Module(DOC‐0177),and/orthePADSCDP‐PBPModule(DOC‐0192)forconfigurationanddisplay
details.
5.0 Dynamic Threshold Feature
TheCDP’sdynamicthresholdfeatureautomaticallyadjuststheinstrument’ssizerandqualifiersignalsto
accountfordriftsduetotemperaturechanges.
5.1 Dynamic Threshold for Sizer Signal
Thedynamicthresholdfeatureworksasfollows.Theinstrument’ssizersignalvoltageisdigitized
witha12‐bitADC,whichyieldsa0to4095count.Ahistogramiscreatedofallcountsbetween0
and512.(Signalsabove512areassumedtoberesponsestoparticles,andthusnotrelevantto
establishingthebaseline.)Thesystemthenidentifiesthenarrowestbandthatcontainsatleast75%
ofcountsinthehistogram.Thisband,referredtoasthe“noiseband,”isthesystem’sattemptto
identifyarangeforbaselinenoisewhennoparticlesarepresent.

Ifthenoisebandexceeds20counts(i.e.,thewidthistoowide),orifnonoisebandwasidentified,
thepreviousnoisebandisused.Thesequalificationsareimposedinordertodistinguishthenoise
fromactualparticleevents.Theinstrumentthenusesthenoisebandtoadjustthesizerbaseline
andidentifyparticles.Thenoisebandupdatesatarateof10Hz.
CDPswithdynamicthresholdingforthesizersignalhavetwoadditionalchannelsincludedintheir
serialdataoutput.DTBandwidthisthewidthofthenoiseband—thatis,[B–A]inFigure5.
DynamicThresholdistheupperboundaryofthenoiseband,i.e.BinFigure5.Bothofthese
channelsaregivenindigitalcounts.


Figure 5: Identifying a Noise Band

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5.2 Dynamic Threshold for Qualifier Signal
Dynamicthresholdingforthequalifiersignalworksexactlyasitdoesforthesizersignal,exceptthat
thequalifiersignalisusedtodeterminethenoisebandandthequalifiersignalissubsequently
adjusted.CDPsthathavedynamicthresholdingforthequalifiersignalhavetwoadditionalchannels
includedintheirserialdataoutput.QualBandwidthisthewidthofthenoiseband—thatis,[B–A]
inFigure5.QualThresholdistheupperboundaryofthenoiseband,i.e.BinFigure5.Bothofthese
channelsaregivenindigitalcounts.
6.0 Instrument Maintenance and Troubleshooting
DMTrecommendsreturningyourinstrumenttothefactoryforanannualcleaningandcalibration.
Thiswillensureyourinstrumentisworkingproperlyandprolongitslifetime.
TheCloudDropletProbeisenvironmentallysealedandiswaterresistantbutnotwaterproof.The
opticalpathisprotectedwiththesapphirewindowsthatcanbeseenthroughthewetlesswindow
ports.Waterresiduecancausecontaminationonthewindowsandthiscontaminationwilldistort
orattenuatetheamountofscatteredlightcollectedfromaparticularparticle.
Tocleanthesapphirewindows,followacceptedopticalcleaningtechniques.Usewhitevinegarona
Q‐tiptoremovewaterspots,thenusealcoholoracetoneforfinalcleaningprocedures.
6.1 Troubleshooting with Housekeeping Channels
SeveraloftheCDP’shousekeepingchannelsofferinformationthathelpsdiagnoseinstrument
health.Thesearedescribedbelow.Forinformationonhowtoconvertthehousekeepinganalog‐
digitalvaluesreturnedbytheCDPintotheunitsgivenbelow,seethesectiononCDPHousekeeping
ChannelsinAppendixD.IfyouhavePADS,theprogramwillhavealreadyperformedthese
conversions.
Laser_Current(mA):Theelectricalcurrentflowingthroughtheinstrument’slaserdiode.Asudden
changeincurrentcouldreflectaproblemwiththeinstrument.Areadingof60–120mAindicates
theinstrumentisfunctioningproperly.Ifthelasercurrentisweakandthelaserbeginspulsing,the
laserhasbecomeoverheated.Acurrentreadingofzeroindicatesafailure.However,atemporary
dropinlasercurrentisnormalwhenanti‐icingheatersareinitiallyturnedon.Ahighlasercurrent
canindicatethelaserisnearingtheendofitslife.
Dump_Spot_Monitor(V):Theamountoffocused,unobstructedlaserlightcollectedinthedump
spotmonitor.Thischannelcanindicateoverallsystemhealth.Ifthemonitorreadinggoesdown
whentherearenoparticlespresent,theremaybeaproblem.(Whenparticlesarepresent,the
laserlightscatters,whichreducesthefocusedlightcollectedinthedumpspot.)Itisimportantto
trackthetrendoveralongperiodoftime,forinstanceoverseveralmonths,asthischannelcan
changeslowly.Overheatedlasersorprobewindowsblockedbyfogand/oricecouldcausethelaser
monitorreadingtogodowneventhoughnoparticlesarepresent.Thedumpspotmonitoris
averagedoverthetiminginterval.
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Wingboard_Temp_(C):ThetemperatureattheCDP’ssignalandpowerdistributionboard.This
temperaturegivesanideaoftheaveragetemperatureoftheprobebody.Wing_Board_Temp
shouldbeafewdegreeshigherthanambienttemperature,sincetheboardisenclosedinthe
instrumenthousingandsincetheanti‐iceheaterswarmit.
Laser_Temp(C):Thetemperatureofthelaserheatsink.TheLaser_Tempreadingshouldbe
relativelystable.HealthyLaser_Tempreadingsare20°‐30°C.
SizerBaseline(V):Thevoltageoutputfromthesizingdetector,whichisperiodicallysampled.This
voltagewillvaryconsiderablybasedonwhetherparticlesarepresentatthetimeofthereading.
Whennoparticlesarepresent,itrangesfrom.2‐.5V.
QualifierBaseline(V):Thevoltageoutputfromthequalifierdetector.Thisvoltage,whichis
periodicallysampled,variesconsiderablybasedonwhetherparticlesarepresentatthetimeofthe
reading.Whennoparticlesarepresent,itrangesfrom.2‐.5V.Itsvalueistypically20‐60mVbelow
thesizerbaseline.
+5VMonitor(V):Thepower5‐voltreferencefortheCDP’scontrolsystem.InPADSthisvoltageis
dividedbytwo,digitized,andmultipliedbytwotoallowaneffective0–10voltrange.Thescaled
valueshouldbe4.75–5.25volts.Valuesoutsidethisrangemayindicateaprobleminthepower
distributionboard.
ControlBoardTemp(C):Thetemperatureatthedigitalboard,whichshouldfallbetween‐40and
+50°C.Valuesoutsidethisrangeindicateapotentialproblemwiththeboard.


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7.0 Calibration
CalibrationoftheCDPistypicallyverifiedwithprecisionglassbeads.Glassbeadsofaknownsize
areinjectedintothesamplearea,andtheinstrumentsizesthem.Theresultingparticle‐size
histogramshouldshowadefinitepeakatasizeslightlysmallerthanthesizeoftheglassbeads.
DMTinstrumentsarecalibratedtomeasurewaterparticles,andwaterandglasshavedifferent
refractiveindexes.Asaresult,theparticlesizesmeasuredbytheinstrumentwillbeabout80%of
theactualsizeoftheglassbeads.TheconversiontableinAppendixBprovidescorrespondingwater
dropletsizesforgivenglassbeadsizes.Thewater‐dropletsizeindicateswherethenumberof
particlesdetectedduringcalibrationtestingshouldpeak.Forinstance,if17‐µmglassbeadsare
usedfortesting,theparticlesdetectedbytheinstrumentshouldpeakatabout14µm.SeeFigure6.


Figure 6: Display of Calibration Test Results. Note the definite peak in the 12-14 µm particle range.

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7.1 Required Equipment
Tocalibrateaninstrumentwithglassbeads,thefollowingequipmentisneeded:
- Canofcompressedgas(alsocalleda“duster”)tocleanthebeaddispenserandcalibration
device.SeeFigure7forexamplesofdusters.Thesearegenerallyavailableatelectronics
supplystoresorcomputerstores.
- Bottleofcertifiedglassbeads,asshowninFigure8.TheseareavailablefromDMT.
- Glassbeaddispenser(DMT#AD‐0164),picturedinFigure9.
- Calibrationfixturefortheinstrument(DMT#ASSY‐0035),designedtokeeptheglassbeads
withintheappropriatedepthoffield.SeeFigure12.
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Figure 7: Compressed Gas Cans or “Dusters”
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Figure 8: Bottle of Glass Beads, DMT OP-0591-0020

DOC-0343 Rev A
© 2017 DROPLET MEASUREMENT TECHNOLOGIES
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7.2 Instructions
1.) Turnontheinstrumentsystempowerandstartthedataacquisitionsystem.
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2.) Usingtheduster,cleantheglassbeaddispenserbyblowingairthroughit(Figure10).Make
surethebottomofthecapandtubesarecleanedasshownontheleftinFigure10.Also
cleanthedispenser’sglasscanisterasshownontheright.
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3.) Cleanthecalibrationdevicewiththedusterbyblowingairdownthetube.
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Note:Steps2and3shouldbeperformedatthestartofeachcalibrationtestsessionand
wheneveranewsizeofglassbeadsisbeingused.Steps2and3maybebypassedforrepeated
testswiththesamesizeofglassbeads.
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Figure 9: Glass Bead Dispenser, DMT AD-0164
Figure 10: Cleaning the Glass Bead Dispenser