Watlow Optimizing Your Process System with the Series 988 Controller - Manual (Page 31)

General Software Features
3.11
Optimizing Your Process System with the WATLOW Series 988
Overview
The remote set point feature allows the 988 to
use a thermocouple, RTD or process signal at
input 2, to establish the set point. This feature
gives the 988 the ability to have its set point
value manipulated by an external source. A
common application would use one ramping
controller with a set-point retransmit output to
ramp multiple 988’s using the remote set point.
Or you could use an analog output from a PLC
to send set point values to a 988. Requirements
Input 2 must be either a thermocouple or
universal signal conditioner, options 1 or 2.
If the application uses a master controller,
choose one of the retransmit options — M (0-
20, 4-20mA) or N (0-5, 1-5 or 0-10VDC) — for
output 3 of the master.
Match input and output impedances.
Remote Set Point
Sample Application
An engineer has a machine with eight independent zones of heat. He wants to
to change set points on all zones without having to adjust each control indi-
vidually. This can be achieved using a 988 with a 0-5VDC retransmit output
as the master controller. The seven remote 988’s will use the 0-5VDC signal
on input 2 as a remote set point. When the set point is changed on the master
controller, the retransmit output changes the set points of the seven remote
controllers. By enabling the ramp to set point feature in the master 988, all
eight zones are ramped up to set point at a user-defined rate on power up.
The retransmit output from the master 988 is set so that 0VDC represents
0
°F and 5VDC represents 800°F. On the remote controllers, set the input 2
DIP switch to the position for the 0-5, 1-5, 0-10VDC process input. In the
Input menu, under the input 2 prompt
, select 0-5. The remote set point
prompt should be set to ON and decimal 2 set to 0. The range
low 2 and the range high 2 parameters will establish the scaling for
the remote set point input. Range low 2 should be set to 0 and range high 2
should be set to 800. To operate a specific zone ten degrees hotter than the
others, increase the range low 2
to 10 and the range high 2 to 810.
With remote set point enabled and local selected under the local-
remote prompt in the System menu, the set point is adjusted using the
increment (up-arrow) and decrement (down-arrow) keys. Selecting remote
under the local-remote prompt
, disables the increment and decrement
keys, allowing the set point value to be manipulated via the input 2 signal.
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
TL
TL
W WA
PROCESS
L1 L2 L3 L4 DEV % OUT DISPLAY
MODE
AUTO MAN
SERIES 988
zone 1 zone 2 zone 3 zone 4 zone 5 zone 6 zone 7 zone 8
Master
Remote Remote Remote Remote Remote Remote Remote
output 3
input 2 input 2 input 2 input 2 input 2 input 2 input 2