Watlow 12LS Controller - Manual (Page 29)

3-15
3.4.1 PID CONTROL AND ALARM OUTPUTS CONNECTIONS
Typical digital control outputs utilize external optically- isolated solid-state relays. These relays use a 3 to 32vdc input
for control and can be sized to switch up to 100 amps at 480vac. For larger currents these relays can be used to drive
contactors.
|-----------------------------------------------------|
¦ NOTE: Control outputs are SINK OUTPUTS. They will be¦
¦low when the output is ON. They should be connected ¦
¦to the minus (-) side of SSRs. ¦
|-----------------------------------------------------|
Example of Heat/Cool And Alarm Outputs Connections:
SSR 1 SSR 2 SSR 3
|------| |------| |------|
RTB TERMINALS PIN ¦ - + ¦ ¦ - + ¦ ¦ - + ¦
|------| |------| |------|
PID HEAT 1 9 ||-------| ¦ ¦ ¦ ¦ ¦
¦ ¦ ¦ ¦ ¦
PID COOL 1 33 ||----------¦---------| ¦ ¦ ¦
¦ ¦ ¦ ¦
+5VDC 1 ||----------|------------|---------¦--|
¦
DIG OUTPUT 1 28 ||---------------------------------|
3.4.2 PID OUTPUT LIMITING
The output from each loop's dual heat/cool output may be limited to a value less than 100%. This level may not be
exceeded by the PID control action. This limit on the control output may be limited by a period of time and than
returned to full 100% output or it may be a continuous limit until changed by the programming keys.
The limit time delay is restarted whenever:
a) A new time period is entered.
b) A loop is switched from MANUAL to AUTO mode.
c) The controller is restarted(powered up).
The time period is adjustable from 1 to 999 seconds for a maximum period of time of over 16 minutes. A time of 0
seconds will be displayed as C, the same as for Continuous.
The Output Limiting is disabled by setting the value to 100%. The control mode of ON/OFF has no output limiting
available.
The output limiting may be used for "Soft Start" type of requirements of different processes. May also be used to
restrict the energy into a process, thus tailoring the controller output to the process requirements.