Rockwell Automation 1746-NR4 SLC RTD/Resistance Input Module User Manual - Manual (Page 95)

Publication 1746-UM008B-EN-P - December 2006
Ladder Programming Examples 95
Use the Proportional
Counts Data Format with
User-set Scaling The RTD module can be set up to return data to the user program that
is specific to the application. Assume that you control 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 ft/m when the
potentiometer is at 0
Ω and 50 ft/m when the potentiometer is at 1000
Ω.
Follow these procedures to configure the RTD module to return a
value between 3…50 in the data word for channel 0.
1. Set bits 0…3 of configuration word 0…1110 to select the 1000
Ω
potentiometer input type.
2. Set bits 4 and 5 of configuration word 0…11 to select
proportional counts data format.
3. Set bits 13 and 14 of configuration word 0…01 to select range 0
as the scaling range.
4. Enter 3 as the low range into N10:4.
5. Enter 50 as the high range into N10:5.
Rung 2:0
] [
COP
COPY FILE
Source
#N10:0
Dest #O:3.0
Length 6
First Pass Bit
S:1
15
Initialize RTD module.
Rung 2:1
SCL
SCALE
Source
I:3.0
Rate [/10000]
Offset
Dest
] [
I:3.4
11
Set speed of conveyor motor Channel 0 Status
Rung 2:2
END
Six elements are copied from the
specified source address (N10:0) to the
specified output (O:30:0). 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…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 SLC 500
Instruction Set Reference Manual,
publication 1747-RM001, or the Analog
I/O User Manual, publication
1746-UM005, for specific examples of
the SCL instruction.