Extech Instruments RPM33 - Taking Measurements; Non-Contact Measurement Procedure; Non-Contact Measurement Considerations

RPM33-EU-EN V1.3 4/13
6
TakingMeasurements
Non‐Contact(Photo)TachometerMeasurements
1. PreparefortheNon‐ContactmeasurementasdescribedintheMeasurementPreparation
sectionabove.
2. UsetheMODEbutton(momentarilypresses)toselectRPM(rotationsperminute)orHz
(Hertz:rotationspersecond)astheunitofmeasure.
3. PressandholdtheMEASUREbuttontobeginameasurementsession.
HoldtheMEASURE
buttondownforthedurationofthetestandreleaseittoendthesession.
4. Pointthemetertowardthedeviceundertestatadistanceof2"to20"(50to500mm).Be
suretoalignthelase rlightbeamwiththereflectivetape(seediagramaboveinprevious
section).
5. Verifythatthe(
(
()
)
)monitorindicatorappearsontheLCDwhenthereflectivetapepasses
throughthelightbeam.
6. ReadthemeasurementresultfromtheLCDdisplay.
7. WhentheMEASUREbuttonisreleasedthelastreadingwillremainonthe
displayfor5to10
secondsbeforethe‘AutoPowerOFF’featureswitchesthemeterOFF.TheHOLDdisplay icon
willswitchON.

Non‐Contact(Phototachometer)MeasurementConsiderations
 Brightambientlightmayinterferewiththereflectedlightbeam.Shadingthetargetarea
maybenecessaryinsomecases.
 Thenon‐reflectiveareamustalwaysbelargerthanthereflectivearea.
 Iftheshaftorrotatingobjectisnormallyreflective,itmustbecoveredwithblacktapeor
paintbeforethereflectivetapeisapplied.
 ToimproverepeatabilityoflowRPMmeasurements,applyadditionalsquaresof
reflectivetape.Dividethereadingshownonthedisplaybythenumberofpiecesof
reflectivetapesquarestocalculatetheactualRPM.

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