M O L B L O C / M O L B O X L O W M A S S F L O W C A L I B R A T I O N S Y S T E M A F M E T C A L
C O N F I G U R A T I O N S
I N S T A L L A T I O N A N D O P E R A T I O N M A N U A L S U P P L E M E N T
©2000-2008
DH Instruments, a Fluke Company
Page 10
D U T S W I T H A N F I T T I N G S
If the DUT can be supported directly from the molstic outlet fittings, then union (2)
and tube (3) can be omitted.
DUTS CALIBRATED WITH BACK PRESSURE
All fittings are connected as shown in Figure 2.
DUTS CALIBRATED WITHOUT BACK PRESSURE
(AT ATMOSPHERIC PRESSURE)
Fittings 6, 7 and 9, and tube 8 and the back pressure regulator can be omitted.
The DUT exhausts directly to atmosphere.
D U T S W I T H S W A G E F I T T I N G S
If the DUT can be supported directly from the molstic outlet fittings, then union (2)
and tube (3) can be omitted.
DUTS CALIBRATED WITH BACK PRESSURE
Since adapting to AN4 is not necessary, fittings 4, 5, 6 and 7 can be omitted.
The 20 in. tube (8) is connected directly to the DUT’s outlet.
DUTS CALIBRATED WITHOUT BACK PRESSURE
(AT ATMOSPHERIC PRESSURE)
Fittings 4, 5, 6, 7 and 9, and tube 8 and the back pressure regulator are all omitted.
C O N N E C T I O N S F O R D U T P R E S S U R E A N D T E M P E R A T U R E M E A S U R E M E N T
Some kinds of DUTs require that flow corrections are made based on the density of
the gas flowing through the DUT during calibration. The density correction is made
from knowledge of the pressure and temperature of the gas as measured near
the DUT. The measurements of pressure and temperature at the molbloc which are
displayed on the molbox and/or COMPASS will not typically be accurate estimates
of the pressure and temperature at the DUT, since the expansion of the gas through
the metering valve can change both the pressure and temperature.
An RPM3-A0100b reference pressure monitor is included in the AFMETCAL
Configuration System to provide accurate DUT pressure measurement. A small back
pressure gauge is also included in the AFMETCAL Configuration Kit, but it will not
generally be accurate enough for DUT pressure measurement and is intended only
for reference indication. Pressure may be read from the RPM3 visually from the
front panel or remotely through a computer connected to it. (See Section 1.1.4 of
this manual, the COMPASS for molbox User’s Manual Version 4.00 and the RPM3
Operation and Maintenance Manual for instructions on operating RPM3 and reading
its pressure measurements via remote interface.)
