DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
© 1998-2003 DH Instruments, Inc .
Page 200
19.13 PRESSURE UNIT CONVERSIONS
COMPASS performs all internal pressure conversion to and from Pascal [Pa], the SI unit for pressure.
Table 70 provides the conversion coefficients used by COMPASS and other DHI products to convert
numerical values expressed in Pascal [Pa] units to corresponding values expressed in other units.
Table 70. Pressure Unit Conversion Chart
TO CONVERT FROM Pa TO MULTIPLY BY
Pa Pascal 1.0
Mbar Millibar 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
User User User defined coefficient
19.14 WATER RATIO
The water ratio is used to correct the flow of a molblocS for the difference between moist and dry Air flow.
The water ratio is never used for laminar molblocs or with gases other than Air. When dry Air is used, the
water ratio should be 0. The water ratio is determined based on the current ambient pressure,
temperature and humidity following Dalton’s Rule and thermodynamic principals using water saturation
properties.
The water ratio is calculed on the <Water Ratio Calculator> . This form is accessed in the [Tools] ,
[Water Ratio Calculator] menu choice. The [Tools] , [Options] , [molbox] tab provides an option to
display this form during test initialization when the reference is a moblocS and the flowing gas is Air (see
Section 11.2).