molbox™ RFM™ OPERATION AND MAINTENANCE MANUAL
© 1998-2007 DH Instruments, a Fluke Company
Page 92
1. High Isolation:
Open
2. Low Isolation:
Open
3. Bypass:
Closed
4. Microrange
Bypass: Open
Figure 11.
molbox RFM
Internal Pneumatic Schematic –
molbloc-S OPERATION, BPR ON
When the molbox RFM internal valves are positioned to allow both RPTs to measure the
molbloc-S upstream pressure, the valve state is referred to as BPR OFF (see Figure 12).
1. High Isolation:
Open
2. Low Isolation:
Closed
3. Bypass:
Open
4. Microrange
Bypass: Open
Figure 12.
molbox RFM
Internal Pneumatic Schematic – molbloc-S OPERATION, BPR OFF
Ideally, the user is able to monitor the BPR with BPR ON while setting flows and pressures, and
once the flow is established, uncertainties can be minimized by turning BPR OFF, gaining the
benefit of using both RPTs upstream. As an alternate to operator switching between BPR ON
and BPR OFF, molbox RFM has a BPR mode called AUTO that uses on-board logic to
determine when to turn BPR ON and OFF. In BPR AUTO mode, the molbox uses cues based on
flow and pressure changes, stability, and proximity to the Reynolds number-based BPR limits to
determine when to switch between the BPR ON and BPR OFF valve states. AUTO is the default
BPR mode and is considered the normal mode for manual molbloc-S/molbox RFM use.
