User manual

PID Loop Operation
(DL450 Only)
Maintenance
8--17
PID Loop Operation (DL450 only)
DL405 User Manual, 4th Edition, Rev. A
Loop 1 Data
V-memory
Output
Module
DL450 CPU
Input
Module
Channel 1
Process 1
Process 2
PV SP OUT
Channel 2
Loop 2 Data
Channel 3
Channel 4
Channel 1
Channel 2
Channel 3
Channel 4
PV SP OUT
After selection and procurement of all loop components and I/O modules, we can
perform the wiring and installation. Refer to the wiring guidelines in Chapter 2 of this
Manual, and to the DL405 Analog I/O Module manual as needed. The most
commonly overlooked wiring details when installing PID loop controls are:
S Reversing the polarity of sensor or actuator wiring connections.
S Incorrect signal ground connections between loop components.
After wiring and installation, choose the loop setup parameters. The easiest method
for programming the loop tables is by using DirectSOFT. This software provides PID
Setup using dialog boxes to simplify the task. Note: It is important to understand
the meaning of all loop parameters mentioned in this chapter before choosing
values to enter.
With the sensor and actuator wiring completed, and loop parameters entered, the
Manual mode must be used to manually and carefully check out the new control
system.
S Verify that the PV value from the sensor is correct.
S If it is safe to do so, gradually increase the control output up above 0%,
and see if the PV responds (and moves in the correct direction!).
If the open loop test (page 8--40) shows the PV reading is good and the control output
has the proper effect on the process; follow the closed--loop auto tuning procedure
(see page 8--45). In this step, the loop is tuned so the PV automatically follows the
SP.
If the closed loop test shows PV will follow small changes in the SP, consider running
an actual process cycle. The programming which will generate the desired SP in real
time must be completed. In this step, it may desirable to run a small test batch of
product through the machine, while watching the SP change according to the recipe.
WARNING: Be sure the Emergency Stop and power-down provision is readily
accessible, in case the process goes out of control. Damage to equipment
and/or serious injury to personnel can result from loss of control of some
processes.
When the loop tests and tuning sessions are complete, be sure to save all loop setup
parameters to disk.
Step 5:
Wiring and
Installation
Step 6:
Loop Parameters
Step 7:
Check Open Loop
Performance
Step 8:
Loop Tuning
Step 9:
Run Process Cycle
Step 10:
Save Loop
Parameters