MKS 246C - External Set Point Control; Figure 5: External Set Point Control Setup - Individual Flow Control

System Configurations Cha
p
ter Two: Installation
28
External Set Point Control
External set point control of the flow rate through MFCs is accomplished using either individual
246 units with an external pressure controller, or multiple units connected for ratio operation with
an external pressure controller and a pressure transducer.
Note
The 246 unit can operate with any controller or pressure transducer
provided the signal that enters the 246 unit goes
positive
with increasing
flow (correct polarity). Throughout this manual, the MKS Type 250
Pressure/Flow Controller is used for example only.
Individual Flow Control
For individual flow control, the system requires the 246 unit, the MFC, an external pressure
controller, and the appropriate cables. To connect the 246 unit to an external controller, connect
the proper interface cable from the external controller to the SP IN jack on the 246 unit (refer to
Figure 5).
"Slave" 246 Unit
(Channel 2)
Window
1
0
10
30
20
40
50
60
7
0
8
0
90
CB246S-2-3
Type 250 Controller
(External Set Point Voltage)
External "Master"
(Channel 1)
Figure 5: External Set Point Control Setup - Individual Flow Control
Note
The drawing in Figure 5 is not drawn to scale.
The flow rate is controlled using a set point signal from the external controller. The external set
point voltage bypasses the 246 unit’s SET POINT CONTROL, and the flow signal is sent
directly to the MFC. Refer to
How To Control Individual Gas Flows with an External Set Point
,
page 62, for operating instructions.