Extech Instruments AN340 Manual

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AN340-EU-EN V1.3 4/13

AREAprogrammingforAirFlow(Volume)CMM/CFMMeasurements

Toaccuratelymeasurethevolumeofairflowinaduct,theareaoftheductmustfirstbemeasured

andtheresultenteredinthemeterviathebuttonpresssequencesdescribedbelow.Refertothe

Appendixformoreinformationonareameasurements,calculations,andunitconversions.Area

measurementsare

enteredassquarecentimetersorsquareinches(cm

orinch

).



Firstdecidethemethodforprogrammingtheareainformationintothe meterandthenproceed.

Thethreemethodsare:



a. LxW:Entertheduct’sLength&Widthmeasurementvaluesincentimetersorinches

(rectangularducts);themeterthencalculatestheareainsquarecentimetersorsquare

inches(cm

orinch

).

b. D:Entertheduct’sDiametervalueincentimetersorinches(forroundducts);themeter

calculatestheareaautomaticallyinsquarecentimetersorsquareinches(cm

orinch

).

c. A:Entertheareavaluedirectlyinsquarecentimetersorsquareinches(cm

orinch

).Seethe

Appendixfortipsonareameasurements,calculations,andunitconversions.



ImportantNote:Areameasurementsmustbeenteredincentimetersorinches.If

measurementsaremadeinmetersorfeetpleaseconverttocentimetersorinches.Seethe

Appendixformoreinformation.



 Fromthenormaloperatingmode,usetheMODEbuttontoscrolltotheAirVolumemode.

 UsetheLW‐D‐Abuttontoselectthemethod:LW(LENGTHxWIDTHforrectangularducts),D

(DIAMETERforcircularducts),orA(AREA:iftheareavalueisknown).ThedisplayiconsL,D,

andAinformtheuserastowhichmodeisselected.

LENGTHxWIDTH(Area)Mode

 Whenthe‘L’isshownatthetopoftheLCD,themeterisreadytoacceptarectangularduct’s

Lengthmeasurementincentimetersorinches.

 Usethe button

ONLYtochangethevalueoftheflashingdigit(pressingthedownarrow

willcausethescreentochangefromLengthtoDiameter).UsetheENTERbuttontomove

fromdigittodigit.

 Whenfinishedenteringthelength,andwiththeright‐mostdigitflashing,presstheENTER

buttontomovetotheWidth(W)screen.

 Whenthe‘W’isshownatthetopoftheLCD,themeterisreadytoaccepttheWidth

measurementincentimetersorinches.

 Usethe buttonONLYtochangethevalue oftheflashingdigit(pressing

thedownarrow

willcausethescreentochangetoDiametermode).UsetheENTERbuttontomovefrom

digittodigit.

 Whenfinishedenteringthewidth,andwiththeright‐mostdigitflashing,presstheENTER

buttontoreturntothemainoperatingmode.

 Themeterautomaticallycalculatesthe areaoftheductand,whenvolumemeasurements

aretaken,theLCDwillshowaccurateairvolume(flow)inCMM/CFMunits.