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Manual: 152-082010 301-305-306_303-307 Series Page 35 of 35
20 / 1.4047 = 14.238
That is, you set the meter to read 14.238 sccm.
Some meters, specifically the high flow meters, are calibrated in air. The flow readings must be
corrected for the case where a gas other than air is flowing through the meter. In addition, there must
be a correction for the difference in the GCF from nitrogen to air. In this case, multiply the reading and
the ratio of the process gas' GCF to the GCF of the calibration gas. For example, a meter calibrated in
air is being used to measure the flow of propane. The reading from the meter is multiplied by the GCF
for propane divided by the GCF of air.
20 * (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 * (1.0015/0.3499) = 57.2449
Gas conversion factors can be found at the Hastings Instruments web site.
http://www.teledyne-hi.com
Follow the link to Mass Flow Products and then to Gas Conversion Factors.