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RPM4™ OPERATION AND MAINTENANCE MANUAL
© 2004-2007 DH Instruments, a Fluke Company Page 136
7.2 UNIT CONVERSION
7.2.1 PRESSURE
RPM4 performs all internal calculations in SI units. Numerical values input or output in other
units are converted to SI immediately after entry and back to other units just before output as
needed.
Table 28 provides the conversion coefficients used by RPM4 to convert numerical values
expressed in SI units to corresponding values expressed in other units.
Table 28. Pressure Unit of Measure Conversion Coefficients
TO CONVERT FROM Pa To MULTIPLY BY
Pa Pascal 1.0
mbar millibar 1.0 E-02
hPa hecto Pascal 1.0 E-02
kPa kilo Pascal 1.0 E-03
bar Bar 1.0 E-05
mmWa @ 4°C millimeter of water 1.019716 E-01
mmHg @ 0°C millimeter of mercury 7.50063 E-03
psi pound per square inch 1.450377 E-04
psf pound per square foot 1.007206 E-06
inWa @ 4°C inch of water 4.014649 E-03
inWa @ 20°C inch of water 4.021732 E-03
inWa @ 60°F inch of water 4.018429 E-03
inHg @ 0°C inch of mercury 2.953 E-04
kcm
2
kilogram force per centimeter square 1.019716 E-05
mTorr milliTorr (micron of mercury 7.50063
Torr Torr (millimeter of mercury) 7.50063 E-3
user User User defined coefficient
Ft feet of altitude
see Altitude Note below
M meter of altitude
see Altitude Note below
Altitude Note: Quantities expressed in units of altitude follow MIL-STD-859A
“Static Pressure, p, in Inches of Mercury for Values of Pressure Altitude, H,
in Geopotential Feet.” MIL-STD-859A provides tables of pressure in inches of mercury
as a function of altitude in feet. RPM4 uses a set of equations to model the
pressure/altitude relationship. The worst case deviation between the MIL-STD-859A
table and the calculated pressure is 0.0001 inches of mercury (0.3 Pa). The pressure
quantity expressed in inches of mercury is converted to Pascal following Table 28 above.
For altitude expressed in meters, meters are converted to feet using 1 m = 3.28084 ft.