Rockwell Automation 1746-NR8 SLC 500 RTD/Resistance Input Module User Manual - Manual (Page 79)

Publication 1746-UM003A-EN-P
Ladder Programming Examples 5-7
Using the Proportional
Counts Data Format
with the User-set Scaling
(Class 3) The RTD module can be set up to return data to the user program that is
specific to the application. Assume that the user controls the line speed of a
conveyor using a 1000
Ω
potentiometer connected to channel 0 of the RTD
module. The line speed will vary between 3 feet/minute when the
potentiometer is at 0
Ω
and 50 feet/minute when the potentiometer is at
1000
Ω
.
Example - Configure the RTD module in Class 3 operation to return a value
between 3 and 50 in the data word for channel 0. Proceed as follows:
1. 1. 1. 1. Set bits 0 through 3 of configuration word 0 to 1110 to select the
1000 Ω potentiometer input type.
2. 2. 2. 2. Set bits 4 and 5 of configuration word 0 to 11 to select proportional counts
data format.
3. 3. 3. 3. Enter 3 as the low range into N10:8.
4. 4. 4. 4. Enter 50 as the high range into N10:9.
Figure 5.7 Programming for PID Applications)
For Class 3 operation registers N10:8 and N10:9 can be used to scale channel 0
for a minimum conveyor speed of 3 ft./minute and a maximum conveyor
speed of 50 ft./minute
] [
COP
COPY FILE
Source
#N10:0
Dest #O:3.0
Length 10
S:1
15
SCL
SCALE
Source
I:3.0
Rate [/10000]
Offset
Dest
] [
I:3.8
11
END
First Pass Bit Initialize RTD module.
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Rung 2:1
Ten elements are copied from the specified source
address (N10:0) to the specified output (O:3.0). Each
element is a 16-bit integer as shown in the data table
at the bottom of the page.
The Source of this instruction is the data word from the
RTD module, which is a number between 3 and 50. The
Dest in this application is an analog output channel
controlling the speed of the conveyor motor drive. The
Rate and Offset parameters should be set per your
application. Refer to the S
LC 500 and MicroLogix 1000
Instruction Set Reference Manual (publication
1747-6.15) or the
Analog I/O User Manual (publication
1746-6.4) for specific examples of the SLC instruction.
Rung 2:2