System Configurations Cha
ter Two: Installation
26
System Configurations
The 246 unit can be configured for manual (internal)
set point control, external set point control,
or remote operation. All connections are made using the connectors on the rear panel (refer to
Figure 8, page 41). The system interface cables are listed in Table 5, page 20.
Manual Set Point Control
Manual set point control of the flow rate through MFCs is accomplished using either individual
246 units or multiple units connected for ratio operation. In either case, the gas flow is based on
the unit’s internal +5 V reference and the unit’s front panel Set Point Control.
Individual Flow Control
For individual flow control, the system requires only the 246 unit, the MFC, and the appropriate
cables. The flow rate is controlled with the front panel SET POINT CONTROL, which is
connected to an internal +5 V reference. Since the +5 V corresponds to full rated flow, the SET
POINT CONTROL can be adjusted up to a maximum of 100% of the rated flow for the attached
MFC. Refer to
How To Manually Control Individual Gas Flows
, page 60, for operating
instructions.
Ratio Flow Control
For ratio flow control, the system requires two or more 246 units connected together, the MFCs,
and the appropriate cables.
To connect multiple 246 units together for ratio operation (refer to Figure 4, page 27):
1. Connect the FLOW OUT jack on the master 246 unit to the SP IN (Set Point In) jack on
the first 246 slave unit.
2. Connect the first slave (Channel 2) 246 unit’s SP OUT (Set Point Out) jack to the next
246 unit’s SP IN jack (Channel 3).
The Set Point In and Set Point Out jacks are internally connected in parallel.
3. Continue to join the slave 246 units together by connecting the SP OUT jack on one unit
to the next 246 unit’s SP IN jack until all of the units are connected.
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