DH Instruments COMPASS FOR MOLBOX, User Manual

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COMPASS

for molbox™ User’s Manual
Page 197
© 1998-2003 DH Instruments, Inc .
Table 65. Definition Of Terms In Flow Unit Conversion Formulas
VARIABLE DESCRIPTION
M
w
Molecular weight of the gas used.
R Ideal gas constant = 8314.411.
T Temperature of the gas or the reference temperature of the flow unit
converted to degrees Kelvin.
P
Pressure of the gas or the reference pressure of the flow unit
converted to Pascal.
Z
(P,T)
Gas compressibility as a function of pressure and temperature.
COMPASS has all of the necessary information to determine
compressibility for the supported calibration gases. When the
conversion is done for non supported gases, 1 is assumed.
ρ
(P,T)
Gas density as a function of pressure and temperature.
s
kg
Flow in kg of gas per second.
sccm
(P,T)
Flow in sccm or ccm at a given pressure and temperature. The only
difference is if the flow unit was setup as an actual flow unit or
volumetrically based mass flow unit. Actual flow units require real
time pressure and temperature information. Volumetrically based
mass flow units reference a constant pressure and temperature.
s
mol
Flow in moles of gas per second.
Table 66. Flow Unit Conversion Scaling Factors
CONVERSION MULTIPLY BY
kg/s to mg/s 1000000
ccm, pccm and sccm to lm, plm, and slm
respectively 0.001
ccm, pccm and sccm to lh, plh and slh
respectively 0.06
ccm, pccm and sccm to cfm, pfm and scfm
respectively 0.0000353147
ccm, pccm and sccm to cfh, pfh and scfh
respectively 0.00211888
ccm, pccm and sccm to m
3
m, pm
3
m, and sm
3
m
respectively
0.000001
ccm, pccm and sccm to m
3
h, pm
3
h, and sm
3
h
respectively
0.00006