MKS 246C, Instruction Manual

Page: 70 / 92

Manual Flow Control Chapter Four: Operation
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Manual Flow Control
Manual (internal) 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 in5 V reference and the unit’s front panel Set Point Control. Refer
to System Configurations, page 26, for installation information.
Note
Ensure that the MFC(s) and the 246 unit(s) are properly configured as
described in How To Setup the System, page 53.
How To Manually Control Individual Gas Flows
This type of operation enables you to manually control individual gas flows based on the unit’s
in5 V set point signal.
1. Set the SET POINT SOURCE SWITCH to the FLOW position.
This connects an in5 V reference to the top of the SET POINT CONTROL.
Since the +5 V corresponds to full rated flow, the Set Point Control can be adjusted up to
a maximum of 100% for the attached MFC’s rated flow.
2. Ensure that the SET POINT CONTROL is properly calculated and adjusted for the MFC
in use.
Refer to step 8, page 57, for an example calculation. The 246 unit is now set to control
the flow of the MFC.
3. Turn the flow ON by placing the FLOW CONTROL SWITCH to the ON position.
The set point signal is applied to the MFC and flow begins after a slight delay. The
correct flow is realized within approximately 1.5 seconds, depending on the type of MFC
being used.
4. Turn the flow OFF by placing the FLOW CONTROL SWITCH to the OFF position.