Publication 1766-RM001A-EN-P - October 2008
Process Control Instruction
357
2.
Connect your process control equipment to your analog modules.
Download your program to the processor. Leave the processor in
the program mode.
3.
Enter the following values: the initial setpoint SP value, a reset T
i
of
0, a rate T
d
of 0, a gain K
c
of 1, and a loop update of 5.
Set the PID mode to STI or Timed, per your ladder diagram. If STI is
selected, ensure that the loop update time equals the STI time
interval.
Enter the optional settings that apply (output limiting, output alarm,
MaxS - MinS scaling, feed forward).
4.
Get prepared to chart the CV, PV, analog input, or analog output as
it varies with time with respect to the setpoint SP value.
5.
Place the PID instruction in the MANUAL mode, then place the
processor in the RUN mode.
6.
While monitoring the PID display, adjust the process manually by
writing to the CO percent value.
7.
When you feel that you have the process under control manually,
place the PID instruction in the AUTO mode.
8.
Adjust the gain while observing the relationship of the output to the
setpoint over time.
9.
When you notice that the process is oscillating above and below the
setpoint in an even manner, record the time of 1 cycle. That is,
obtain the natural period of the process.
Natural Period
≅
4x deadtime
ATTENTION
Ensure that all possibilities of machine motion have been considered with
respect to personal safety and equipment damage. It is possible that your
output CV may swing between 0 and 100% while tuning.
TIP
If you want to verify the scaling of your continuous system and/or
determine the initial loop update time of your system, go to the procedure
on page 358.
efesotomasyon.com - Allen Bradley,Rockwell,plc,servo,drive
