Useful Equations And Conversions - Extech Instruments AN100-NIST User Manual

Useful Equations and Conversions

Area equation for rectangular or square ducts
Width (W)
Area equation for circular ducts
Radius
Cubic equations
CFM (ft
CMM (m
must be converted to feet or meters before using the above formulae.
Unit of Measure Conversion Table
1 m/s
1 ft/min
1 knot
1 km/h
1 MPH
Height (H)
Area (A) = Width (W) x Height (H)
Area (A) =
Where
3
/min) = Air Velocity (ft/min) x Area (ft
3
/min) = Air Velocity (m/sec) x Area (m
NOTE: Measurements made in inches
m/s ft/min
1 196.87
0.00508 1
0.5144 101.27
0.2778 54.69
0.4464 87.89
π
2
x r
π
2
= 3.14 and r = radius x radius
knots
1.944
0.00987
1
0.54
0.8679
10
2
)
2
) x 60
km/h MPH
3.6 2.24
0.01829 0.01138
1.8519 1.1523
1 0.6222
1.6071
AN100-en-GB_V3.6 6/18
1