Useful Equations And Conversions - Extech Instruments HD300 User Manual

Useful Equations and Conversions

AREA equation for rectangular or square ducts
Width (W)
Area equation for circular ducts
Cubic equations
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)
Radius
3
CFM (ft /min) = Air Velocity (ft/min) x Area (ft
3
CMM (m /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
Area (A) = Width (W) x Height (H)

2
Area (A) =
x r


= 3.14 and r
Where
knots
1.944
0.00987
1
0.54
0.8679
10
2
= radius x radius
2
)
2
) x 60
km/h MPH
3.6 2.24
0.01829 0.01138
1.8519 1.1523
1 0.6222
1.6071
HD300-EU-EN V2.2 07/13
1