Instruction Manual

56 SLC 500
™
Universal Analog Input Module
Interfacing to the PID
Instruction
The universal module was designed to interface directly to the SLC
5/02™ or later processor PID instruction without the need for an
immediate scale operation.
Example - Use NI8u channel data as the process variable in the PID
instruction.
1. Select scaled-for-PID as the data type in the channel configuration
word.
2. Specify the input channel data word as the process variable for the
PID instruction.
In this example, the value -32,617 is the numeric equivalent of
configuration word N10:0 for channel 0. It is configured for a type K
thermocouple, scaled-for-PID, zero the signal for an open circuit, 10
Hz, °C, channel enabled, to return the data word.
Figure 5.8 Programming for PID Control Example
MOV
MOVE
Source N10:0
-32,617
Dest O:3.0
0
First Pass Bit Initialize NI8u
Channel 0
s:1
] [
15
PID
PID
Control Block N11:0
Process Variable I:3.0
Control Variable N11:23
Control Block Length 23
SCL
SCALE
Source N11:23
Rate [/10000]
Offset
Dest
Rung 2:0
Rung 2:1
Rung 2:2
Rung 2:3
I
END
I
Program Listing
The Rate and Offset parameters should be set per
your application. The Dest will typically be an
analog output channel. Refer to the APS User Manual
or Analog I/O Modules User Manual for specific
examples of the SLC instruction.