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For example, to get a desired flow of 20 sccm of argon flowing through the meter, divide 20
sccm by 1.3978
20.000 / 1.3978 = 14.308
That is, you ` (adjust the gas flow) to read 14.308 sccm.
Some meters, specifically the high flow meters, are calibrated in air. The flow readings must
then be corrected twice. Convert once from air to nitrogen, then from nitrogen to the gas that
will be measured with the meter. In this case, multiply the reading times the ratio of the
process gas’ GCF to the GCF of the calibration gas.
Example:
A meter calibrated in air is being used to flow propane. The reading from the meter is
multiplied by the GCF for propane and then divided by the GCF of air.
20 x (0.3499/1.0015) = 6.9875
To calculate a target setting (20 sccm) to achieve a desired flow rate of propane using a meter
calibrated to air, invert the ratio above and multiply.
20 x (1.0015/0.3499) = 57.2449
Gas Conversion Table for Nitrogen
Rec
# Gas Symbol GCF Derived
Density
(g/L) Z
25° C / 1
atm
1 Acetic Acid C
2
H
4
F
2
0.4155 4 2.700 2.0301
2 Acetic Acid, Anhydride C
4
H
6
O
3
0.2580 4 4.173 2.3384
3 Acetone C
3
H
6
O 0.3556 4 2.374 1.7504
4 Acetonitryl C
2
H
3
N 0.5178 4 1.678 1.4462
5 Acetylene C
2
H
2
0.6255 4 1.064 0.9792
6 Air Air 1.0015 1 1.185 1.0930
7 Allene C
3
H
4
0.4514 4 1.638 1.3876
8 Ammonia NH
3
0.7807 2 0.696 0.6409
9 Argon Ar 1.4047 1 1.633 2.1243
10 Arsine AsH
3
0.7592 5 3.186 4.0839
11 Benzene C
6
H
6
0.3057 4 3.193 2.0636
12 Boron Trichloride BCl
3
0.4421 4 4.789 3.6531
13 Boron Triflouride BF
3
0.5431 4 2.772 2.4109
14 Bromine Br
2
0.8007 4 6.532 1.0000
15 Bromochlorodifluoromethane CBrClF
2
0.3684 4 6.759 4.2789
16 Bromodifluoromethane CHBrF
2
0.4644 4 5.351 4.3990
17 Bromotrifluormethane CBrF
3
0.3943 4 6.087 4.1546
18 Butane C
4
H
10
0.2622 2 2.376 1.6896
19 Butanol C
4
H
10
O 0.2406 4 3.030 1.9233
20 Butene C
4
H
8
0.3056 4 2.293 1.6700
21 Carbon Dioxide CO
2
0.7526 1 1.799 1.7511
22 Carbon Disulfide CS
2
0.6160 4 3.112 3.0744
23 Carbon Monoxide CO 1.0012 4 1.145 1.0433
24 Carbon Tetrachloride CCl
4
0.3333 4 6.287 3.6196
25 Carbonyl Sulfide COS 0.6680 4 2.456 2.4230
26 Chlorine Cl
2
0.8451 4 2.898 3.9995
27 Chlorine Trifluoride ClF
3
0.4496 5 3.779 2.8970
28 Chlorobenzene C
6
H
5
Cl 0.2614 4 4.601 2.4954
29 Chlorodifluoroethane C
2
H
3
ClF
2
0.3216 4 4.108 2.5119