Aalborg GFC - Manual (Page 15)

Setpoints are controlled locally or remotely. Setpoints inputs respond to analog 0
to 5 VDC or 4 to 20 mA reference voltages (default jumper setting is 0 to 5 VDC).
Voltage is a linear representation of 0 to 100% of the full scale mass flow rate.
Response times to setpoint changes are 1 second (GFC 17), 2 seconds (GFC
37/47) and 5 seconds (GFC 57/67/77) within 2% of the final flow over 25 to 100%
of full scale.
For LOCAL flow control, use the built-in setpoint potentiometer located at the
same side as the solenoid valve of the GFC transducer. While applying flow to
the transducer, adjust the setpoint with an insulated screwdriver until the flow
reading is the same as the desired control point. [Display will only show actual
instantaneous flow rates. There is no separate display for setpoints].
For REMOTE control of the GFC, an analog reference signal must be supplied.
On pin [11] of the GFC transducer is a regulated and constant +5VDC output sig-
nal. This signal may be used in conjunction with a local setpoint potentiometer
for flow setting.
FIGURE 5-1 LOCAL SETPOINT POTENTIOMETER CONNECTIONS
It is recommended that a potentiometer between 5K to 100K ohm and capable of
at least 10-turns or more for adjustment be used. Use the control potentiometer
to command the percentage of flow desired.
Alternatively, a variable 0 to 5VDC or 4 to 20 mA analog signal may be applied
directly to the SETPOINT and COMMON connections of the GFC transducer (see
Figure 2-1). Be sure to apply the appropriate signal for the designated jumper set-
tings.
5.5 Valve OFF Control
(Open Collector NPN Compatible)
It may be necessary or desirable to set the flow and maintain that setting while
being able to turn the flow control valve off and on again. Closing of the valve
(without changing the setpoint adjustment) can be accomplished by connecting
pin [12] of the 15-pin “D” connector to COMMON pin [3]. When pin [12] is con-
nected to COMMON, the solenoid valve is not powered and therefore will remain
normally closed regardless of the setpoint. The Motorized valve will be given the
command to close indicated by a green light on top of the unit.
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