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4.5 PC Connections
a. Connection through Flow Readout Box with PC or other external signal. (Figure 9)
Figure9. Connection with PC through Readout Box
When need test the output signal Voltage(0-5VDC), users could connect to the “Flow Signal Output” and the
“Signal common” of external control signal socket of Flow Readout Box, also could directly connect with PC
modulus (A/D) converter, +5.00 V output voltage is corresponding as full scale rating flow rate of MFC. Please
be sure the flow testing output electric current will be no more than 3mA.
When the flow is setting by external signals , it should be turned the switch on “OUT”, meanwhile, it should be
input 0-5.00VDC external voltage from external control socket to the Flow Readout Box. In case of user’s
external potentiometer had settled, it could be used a 3.3K multi-turn potentiometer to connect to the external
control signal socket of “+5.00V” and “signal common”. It also could be directly connecting with modulus (D/A)
converter of PC to achieve auto-control, please be sure the flow setting input resistance should be higher than
100 KΩ.
If PC or PLC need perform the OFF and PURGE function of valve control, it could be accomplished by use two
RELAYS (two sets) transfer contacts. One relay controls OFF and anther one controls PURGE, when these two
relays are not operating then it reaches to auto-control mode. Please be careful, it should be not caused short
circuit by two relays simultaneously operating. Suggested relays connection as method as showing in Figure 11.
MFC or
MFM
Readout Box
Connection
Cable
Flow Signal Output
EXT
Signal common
Valve drive
A/D In
Signal common
D/A Out
Signal common
+15V
Off
-15V
Purge
COMPUTER
Or PLC
(ATTENTION:
No “Valve drive” and
“Set” in MFM )
INT
SET
Auto
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