Omron CJ Series Operation Manual page 28

Introduction and Features
Control Operation
(Forward and Reverse)
Input Compensation
Function
Heater Burnout Detection
(Single-phase Operation
Only)
Two Internal Alarms for
Each Loop
Store Settings in EEPROM
Note The "limit-cycle method" uses ON/OFF operation to cause hunting around the
SV, measures the amplitude and hunting period, and calculates the optimum
PID constants.
The Temperature Control Unit's control can be set to reverse operation or for-
ward operation with pins 4 and 5 of the Unit's DIP switch. The factory setting is
for reverse operation (heating).
One forward/reverse setting controls the operation of loops 1 and 3, and the
other forward/reverse setting controls the operation of loops 2 and 4.
With forward operation (cooling), the manipulated variable is increased as the
PV increases. With reverse operation (heating), the manipulated variable is
increased as the PV decreases.
Manipulated variable
100%
0%
Low SV
temperature
Forward operation
For example, when heating control is being performed and the present tem-
perature (PV) is lower than the target temperature (SP), the manipulated vari-
able is increased as the difference between the PV and SP increases.
Consequently, heating control uses "reverse operation" and cooling control
uses "forward operation."
This function adjusts the PV by adding an input compensation value to the
temperature measured by the sensor.
If you have an application where you want to control and display the tempera-
ture at a point that is offset from the sensor's measurement point, use this
function to control the temperature at a value near the desired point.
When a Two-loop Temperature Control Unit is being used, a Current Trans-
former (CT) can be connected to each loop to detect a heater burnout.
There are two internal alarms per loop. Alarms can be output to the allocated
areas in the CPU Unit's memory areas and any one of the following 9 alarm
modes can be used:
Upper and lower-limit alarm, upper-limit alarm, lower-limit alarm, upper and
lower-limit alarm with standby sequence, upper-limit alarm with standby
sequence, lower-limit alarm with standby sequence, absolute-value upper-
limit alarm, and absolute-value lower-limit alarm
Various Temperature Control Unit settings, such as the alarm SVs and PID
constants, can be stored in the Unit's EEPROM using a control bit in the CPU
Unit's allocated memory area.
Also, it is possible to set the Temperature Control Unit so that the settings
stored in EEPROM are automatically written to the appropriate area in the
CPU Unit when the power is turned ON or the Unit is restarted. This automatic
transfer function is controlled by a switch (pin 8 of the DIP switch) on the front
of the Temperature Control Unit.
Manipulated variable
100%
0%
Low
High
temperature
temperature
Section 1-1
High
SV
temperature
Reverse operation
5