Rockwell Automation 1761-HHP-B30 MicroLogix 1000 with Hand-Held Programmer (HHP) - Manual (Page 180)

Chapter 10
Using Math Instructions
10–14
The following example takes a 0V to 10.5V analog input from a MicroLogix 1000
analog controller and scales the raw input data to a value between 0 and 100%. The
input value range is 0V to 10V which corresponds to 0 to 31,207 counts. The scaled
value range is 0 to 100 percent.
Application Example – Convert Voltage Input to Percent
Scaled Value
(percent)
Input Value
0V 31,207 10V
100
(Scaled Max.)
(Scaled Min.)
(Input Min.) (Input Max.)
0
Calculating the Linear Relationship
Use the following equations to calculate the scaled units:
Scaled value = (input value x rate)
+
offset
Rate = (scaled max. – scaled min.) / (input max. – input min.)
= (100 – 0) / (31,207 –
0
)
= .00320 (or 32/10000)
Offset = scaled min. – (input min. x rate)
= 0
−
(0
×
.00320)
=
0
As shown below, if the input value is 10, the scaled value is .032.
.032 = (10 x .0032) + 0
SCL
SCALE
Source
I:0.4
Rate [/10000] 32
Offset 0
Dest N7:0
Ladder representation: