Extech Instruments AN340 Manual

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AN340-EU-EN V1.3 4/13

Appendix:UsefulEquationsandConversions

Areaequationforrectangularorsquareducts

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Areaequationforcircularducts

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Cubicequations

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NOTE:Measurementsmadeininchesorcentimetersmustbeconvertedtofeetormetersbeforeusingtheseformulae.

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UnitofMeasureConversionTable

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 m/s ft/min knots km/h MPH

1m/s 1 196.87 1.944 3.6 2.24

1ft/min 0.00508 1 0.00987 0.01829 0.01138

1knot 0.5144 101.27 1 1.8519 1.1523

1km/h 0.2778 54.69 0.54 1 0.6222

1MPH 0.4464 87.89 0.8679 1.6071 1

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Area(A)=Length(L)xWidth(W)

CFM(ft

/min)=AirVelocity(ft/min)xArea(ft

)

CMM(m

/min)=AirVelocity(m/sec)xArea(m

)x60

Radius

Area(A)=pi xr

Wherepi=3.14andr

=radiusxradius

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Diameterofcircle=radiusx2

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