Alicat VC Series Volumetric Flow Controller User Manual
Page 20
20
Serial refers to a remote digital RS-232 set-point applied via a serial connection to a computer or
PLC as described in the Installation and RS-232 sections of this manual.
CAUTION! N
ever
leave
a
C
oNtroller
with
aNy
NoN
-
zero
set
-
poiNt
if
No
pressure
is
available
to
make
flow
. t
he
CoNtroller
will
apply
full
power
to
the
valve
iN
aN
attempt
to
reaCh
the
set
-
poiNt
. w
heN
there
is
No
flow
,
this
CaN
make
the
valve
very
hot!
Local refers to a set-point applied directly at the controller. For more information on changing the
set-point locally refer to the heading “Select” below. Local input must be selected prior to attempting
to change the set-point locally.
CAUTION! N
ever
leave
a
C
oNtroller
with
aNy
NoN
-
zero
set
-
poiNt
if
No
pressure
is
available
to
make
flow
. t
he
CoNtroller
will
apply
full
power
to
the
valve
iN
aN
attempt
to
reaCh
the
set
-
poiNt
. w
heN
there
is
No
flow
,
this
CaN
make
the
valve
very
hot!
Select – To avoid accidental changing of the PID loop parameters or the set-point, the Control Setup
mode defaults with the selector on a null position. To change the set-point or the P and D PID loop
parameters, push the button in the upper left corner just above the dynamic label “Select” until the
selection arrow is pointing to the parameter you wish to change. When the parameter you wish to
change is selected, it may be adjusted up or down with the buttons under the display below the dynamic
labels “UP” and “DOWN”. Press the buttons repeatedly to make slow adjustments or hold them down
to make fast adjustments.
P refers to the Proportional term of the PID loop. Before changing this parameter, it is good practice to
write down the initial value so that it can be returned to the factory settings if necessary.
D refers to the Differential term of the PID loop. Before changing this parameter, it is good practice to
write down the initial value so that it can be returned to the factory settings if necessary.
AUT0on / AUT0off refers to the standard auto-tare or “auto-zero” feature. It is recommended that the
controller be left in the default auto-tare ON mode unless your specific application requires that it be
turned off. The auto-tare feature automatically tares (takes the detected signal as zero) the unit when it
receives a zero set-point for more than two seconds. A zero set-point results in the closing of the valve
and a known “no flow” condition. This feature helps to make the device more accurate by periodically
removing any cumulative errors associated with drift.
Set refers to the Set-point. This parameter may only be changed if “Local” is selected as the Input. See
above for information on selecting the input. Using the UP and DOWN buttons, the set-point may be
adjusted between zero and the full-scale range of the controller.
CAUTION! N
ever
leave
a
C
oNtroller
with
aNy
NoN
-
zero
set
-
poiNt
if
No
pressure
is
available
to
make
flow
. t
he
CoNtroller
will
apply
full
power
to
the
valve
iN
aN
attempt
to
reaCh
the
set
-
poiNt
. w
heN
there
is
No
flow
,
this
CaN
make
the
valve
very
hot!
Gas Select Mode
The Gas Select Mode is accessed by pressing the button above “Gas Select” on the Select Menu
display. The screen will appear as shown in Figure 9 (page 13). The selected gas is displayed on the
default main mode screen as shown in Figure 12, and is indicated by the arrow in the gas select mode
screen in Figure 9. To change the selected gas, use the buttons under “UP” and “DOWN” or those
above “PgUP” and “PgDWN” to position the arrow in front of the desired gas. When the mode is cycled
back to the main mode, the selected gas will be displayed on the main screen.
Note: Gas Select Mode may not be available for units ordered for use with a custom gas or blend.