molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL
© 1998-2007 DH Instruments, a Fluke Company
Page 18
Operating at pressures other than those of the molbloc-L pressure dependent calibration type
(see Section 1.2.4.1.2) or molbloc-S calibration type (see Section 1.2.4.2.2) may result in
out of tolerance flow measurements. Refer to the molbloc Calibration Report to
determine its calibration type.
2.3.5
VACUUM SUPPLY (molbloc-S ONLY)
In some cases molbloc-S is operated with a vacuum downstream of the molbloc to reduce the back
pressure so that critical flow can be reached at a lower upstream pressure (see Section 3.1.2).
There is no lower limit to the pressure that may safely be applied to molbox RFM RPTs.
If you are using DHI supplied downstream vacuum connect kit and vacuum pump:
Install the kit and pump following the supplied instruction sheet or manual. Carefully follow
the pump manufacturer’s recommendations for pump operation.
If you are NOT using DHI supplied downstream vacuum connect kit and vacuum
pump:
Carefully evaluate vacuum pump specifications to be sure that the vacuum source
available has the pumping speed necessary to safely handle the planned flows and to
maintain low enough pressure at planned flow rates.
Be sure to provide facilities to avoid flowing into the pump when the pump is not ON as this
will cause pressure to build up on the pump and may damage it. Normally, a shut-off valve
should be included between the pump and the molbloc-S.
It is preferable to install a check valve with very low cracking pressure between the molbloc
and the vacuum shut-off valve.
Adaptor kits are available from
DHI
to make connections from the molbloc or molstic fittings
to other common connector types. Ask you
DHI
Sales Representative about your specific
adaptor requirements.
Operating at pressures other than those of the molbloc-S calibration type may result in
out of tolerance flow measurements (see Section 1.2.4.2.2). Refer to the molbloc
Calibration Report to determine its calibration type.
2.3.6
COMMUNICATIONS CONNECTIONS
If molbox RFM is being interfaced to a computer, connect an RS232 cable to molbox RFM
COM1 or an IEEE-488 cable (cables not supplied) to the molbox RFM IEEE-488 interface.
Configure the interface (see Section 3.6.6).
2.4
POWER UP AND VERIFICATION
2.4.1
POWER UP
Connect the molbox RFM power cable to an electric supply of 85 to 264 VAC (47 to 440 Hz).
Observe the front panel display as molbox RFM initializes, error checks, calibrates its internal
ohmic measurement system and goes to the main run screen (see Section 3.2). The top left
side of the main run screen should display a flow value near zero or
<BPR HI>
. If
<NO
BLOC>
is displayed, molbox RFM has not been able to identify a molbloc connection and
load molbloc information. Verify that a valid molbloc is properly connected (see Section
2.3.3) and press
[SETUP]
,
<4molbloc>
to load the molbloc data. If molbox RFM is still
unable to identify a molbloc, the molbloc may require reloading of EEPROM information or
molbox RFM may require repair.
