MFC-CB™ Operation and Maintenance Manual
©2001~2007
DH Instruments, a Fluke Company
Page 16
3.2
DIRECT FUNCTION KEYS
3.2.1
[K]
PURPOSE
To specify a gas measurement conversion factor,
K
, to be applied to the active device
channel when using and MFC or MFM calibrated with one gas to set and/or measure the
flow of another gas.
PRINCIPLE
MFCs and MFMs respond differently to different gas species due the different specific
heats of the gases and different behavior in the device. Therefore, the calibration of an
MFC or MFM with one gas may not be valid with another gas. MFC manufacturers often
provide gas conversion factors, known as K factors, to convert an MFC from the gas it
was calibrated with to another gas.
The MFC-CB’s K function allows the device manufacturer’s K factor to be entered and
applied to the active channel so that set points and measurement values are
automatically adjusted by the K factor. This feature can be useful when using an MFC
calibrated with one gas to control or measure a different gas.
MFC-CB applies the K factor only when the unit of measure is a flow unit. When the unit
of measure is an electrical unit (V or mA) or %FS, the K factor has no effect.
See Section 7.1.1 for details on the calculations used to apply the K factor.
When using MFC-CB in conjunction with a molbox/molbloc mass flow standard to calibrate
or verify an MFC, the K factor function of the MFC-CB is NOT normally used. K factors are
applied to the molbox measured flow to simulate a process gas with a surrogate gas (see
the molbox Operation and Maintenance manual Section concerning K factors).
OPERATION
To enable a
gas conversion factor
press
[K]
from the
MAIN run screen. The display is:
If
<2off>
is selected, no conversion factor will
be applied. If
<1on>
is selected, the next screen is:
K factor:
1.00000 D1
K factor: (1.0000)
1off 2on D1
