Omega FMA 4000 User Manual
Page 41
9.3 Technical
Assistance
OMEGA
7 Engineering will provide technical assistance over the phone to quali-
fied repair personnel. Please call our Flow Department at 800-872-9436 Ext.
2298. Please have your Serial Number and Model Number ready when you call.
37
Q
O2
= Q
a
= Q
r
X K = 1000 X 0.9926 = 992.6 sccm
where K = relative K factor to reference gas (oxygen to nitrogen)
1
d X C
p
where d = gas density (gram/liter)
C
p
= coefficient of specific heat (cal/gram)
Q
a
K
a
Q
r
K
r
where Q
a
=
mass flow rate of an actual gas (sccm)
Q
r
=
mass flow rate of a reference gas (sccm)
K
a
=
K factor of an actual gas
K
r
=
K factor of a reference gas
=
10.
CALIBRATION CONVERSIONS FROM
REFERENCE GASES
The calibration conversion incorporates the K factor. The K factor is derived from
gas density and coefficient of specific heat. For diatomic gases:
=
K
=
K
gas
Note in the above relationship that d and Cp are usually chosen at the same con-
ditions (standard, normal or other).
If the flow range of a Mass Flow Meter remains unchanged, a relative K factor is
used to relate the calibration of the actual gas to the reference gas.
For example, if we want to know the flow rate of oxygen and wish to calibrate
with nitrogen at 1000 SCCM, the flow rate of oxygen is:
Note: If particular K factor is activated via digital interface, the user
does not need to perform any conversion. All conversion computations
will be performed internally by MCU.