MKS 1579A, Instruction Manual

Page: 63 / 87

1579A//579A Chapter 8: Gas Correction Factor (GCF)
63
Example
Calculate the GCF for a gas mixture of argon (gas 1) flowing at 150 sccm and nitrogen (gas 2)
flowing at 50 sccm, where:
Argon (Ar) Nitrogen (N
2
)
a
1
= 150 = 0.75 a
2
= 50 = 0.25
200 200
s
1
= 1.030 s
2
= 1.000
d
1
= 1.782 g/l d
2
= 1.250 g/l
cp
1
= 0.1244 cal/g ° C cp
2
= 0.2485 cal/g ° C
GCF
M =
(0 .3 1 0 6 ) [(0 .7 5
(0 .7 5 )(1 .7 8 2 )(0 .1 2 4 4
)(1 .0 3 0 ) + (0 .2 5 )(1 .0 0 0 )]
) + (0 .2 5 )(1 .2 5 0 )(0 .2 4 8 5 )
=
(0 .3 1 0 6 )
(0 .1 6 6
[(0 .7 7 2 5 ) + (0 .2 5 )]
3 ) + (0 .0 7 7 7 )
=
(0 .3 1 0 6 ) (1 .0 2 2 5 )
0 .2 4 4
=
0 .3 1 7 6
0 .2 4 4
= 1 .3 0 2
GCF
M
Mass Flow Rate at a Different Reference Temperature
The equations for calculating the GCF assume that the MFC was calibrated at a reference
temperature of 0° C (~273,15 K). If you want to read the mass flow as if the MFC was calibrated at
a different reference temperature, adjust the calculated GCF value using the following equation:
GCF
X
N
x
T
T
x GCF =
where:
Tx = actual reference temperature in °C
T
N
= international standard temperature 0° C