MKS 247D - Manual Flow Control; How To Manually Control Individual Gas Flows

Chapter Four: Operation Manual Flow Control
59
Manual Flow Control
Manual control of the flow rate through MFCs in an
individual
or
ratioed
mode is accomplished
using the system configuration shown in Figure 3, page 27.
Note
Ensure the MFCs and the 247 unit are
p
ro
p
erl
y
confi
g
ured as described in
How To Setup the System,
page 55
.
How To Manually Control Individual Gas Flows
This mode of operation enables you to control individual gas flows using an internal set point
signal.
1. Move the CHANNEL SELECTOR to position 1.
2. Ensure the SET POINT SOURCE SWITCH is set to the FLOW position.
This connects an internal +5 V reference to the top of the SET POINT CONTROL.
Since the +5 V corresponds to full rated flow, each Set Point Control can be adjusted up
to a maximum of 100% for the attached MFCs rated flow.
3. Adjust the SET POINT for the MFC.
Hold the READ/SET POINT SWITCH in the SET POINT position and turn the SET
POINT CONTROL to the desired level as displayed on the Digital Panel Meter. When
the adjustment is complete, release the READ/SET POINT SWITCH; it is spring loaded
and will return to the READ (Flow) position.
Since the Digital Panel Meter is driven from the scaled output, the displayed value has
the Gas Correction and Gauge Factors applied.
Therefore, it represents the actual set
point in sccm for the attached MFC
. Refer to
Scaling Controls
, page 46, for more
information.
4. Move the CHANNEL SELECTOR to the next channel position that has an MFC
connected to it, and repeat steps 2 and 3 until the set points for all channels with MFCs
attached have been properly set.
5. Return the CHANNEL SELECTOR to the channel that you wish to monitor.
The system is now completely adjusted to set the flow of each MFC.