Rockwell Automation 1746-FIO4V SLC 500 Fast Analog I/O/ User Manual - Manual (Page 44)

Publication 1746-UM009B-EN-P - September 2007
44 Write Ladder Logic
Scale an Analog Input and
Detect an Out-of-range
Condition The following example shows input range checking and scaling the
analog input to engineering units for a 1746-FIO4V analog input
module.
We are making the following assumptions:
• The 1746-FIO4V module is located in slot 3 of a modular system.
• A pressure sensor with a 0…10V dc output is wired to input
channel 1.
• The sensor signal voltage is proportional to a range of
100…500 PSI.
• The process pressure must stay between 275…300 PSI.
(If the pressure deviates from this range, your logic sets an alarm
bit.)
• Data is presented in PSI for monitoring and display purposes.
Input Scaling
The scaling operation is displayed in the following graph. It displays
the linear relationship between the input and the resulting scaled
values.
Input Scaling
500 PSI
(scaled max)
100 PSI
(scaled min)
300 PSI
275 PSI
Scaled
Value
Input Value
Process operating range
4095 = 10V dc
(input max) High
Limit Low
Limit 0 = 0V dc
(input min)