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User Manual
GFK-1503F
The configurable words of the reference array must be specified before executing the PID
function. Zeros can be used for most default values. Once suitable PID values have been
chosen, they can be defined as constants in BLKMOV functions so the program can set and
change them as needed.
The PID function does not pass power flow if there is an error in the configurable parameters.
The function can be monitored using a temporary coil while modifying data.
Note:
14.2.1
Scaling Input and Outputs
All parameters of the PID function are 16 bit integer words for compatibility with 16 bit
analog process variables. Some parameters must be defined in either PV counts or units or
in CV counts or units.
The SP input must be scaled over the same range as the PV, because the PID function
calculates error by subtracting these two inputs.
The process PV and control CV counts do not have to use the same scaling. Either may be -
32000 or 0 to 32000 to match analog scaling, or from 0 to 10000 to display variables as
0.00% to 100.00%. If the process PV and control CV do not use the same scaling, scale factors
are included in the PID gains.
14.2.2
Reference Array Parameters
The reference array parameters are described on the following pages. The Machine Edition
software allows you to modify the configurable parameters for a PID instruction in real time
in online programmer mode. To customize PID parameters, right click the PID function and
select Tuning.
Words
1
(Address + 0)
2 (Address + 1)
PID Built-in Function Block
If you set the Override bit (bit 0) of the Control Word (word 15 of the reference array) to 1,
the next four bits of the control word must be set to control the PID function block input
contacts, and the Internal SP (word 16) and Internal PV (word 18) must be set because you
have taken control of the PID function block away from the ladder logic.
Parameter/Description
Loop Number
Optional number of the PID block. It provides a
common identification in the CPU with the loop
number defined by an operator interface
device.
Algorithm
1 = ISA algorithm
2 = independent algorithm
Chapter 14
Jan 2020
Low Bit
Range
Units
Integer
0 to 255 (for
user display
only)
-
Set by the
CPU
251
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