User guide

Chapter 26
PID Instruction
26–19
The Manual Mode
In the manual mode, the PID algorithm does not compute the value of the
control variable. Rather, it uses the value as an input to adjust the integral
sum (words 17 and 18) so that a bumpless transfer takes place upon
re-entering the AUTO mode.
In the manual mode, the HHT allows you to enter a new CO value from 0 to
100%. This value is converted into a number from 0 to 16383 and written to
the Control Variable address. If you are using an analog output module for
this address, you must save (compile) the program with the File Protection
option set to None. This allows writing to the output data table. If you do
not perform this save operation, you will not be able to set the output level in
the manual mode. If your ladder program sets the manual output level,
design your ladder program to write to the CV address when in the manual
mode. Note that this number is in the range of 0 to 16383, not 0 to 100.
Writing to the CO percent (word 16) with your ladder program has no effect
in the manual mode.
The following is an example that can be used to control the output (CV) with
your ladder program.