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Calculating the linear relationship -2, Calculating the linear relationship – Rockwell Automation 1746-XXXX SLC 500 4-Channel Analog I/O Modules User Manual User Manual

Page 64

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Publication 1746-UM005B-EN-P - June 2004

6-2 Programming Examples

The scaling operation is displayed in the following graph. It displays
the linear relationship between the input and the resulting scaled
values.

Calculating the Linear Relationship

Use the following equations to express the linear relationship between
the input value and the resulting scaled value.

Scaled value = (input value x slope) + offset

Slope = (scaled max. - scaled min.) / (input max. - input min.)

(500 - 100) / (32,767 - 0) = 400/32,767

Offset = scaled min. - (input min. x slope)

100 - (0 x (400/32,767)) = 100

Scaled value = (input value x (400 / 32767)) + 100

Scaled

Value

0=0V dc

(input min.)

Low

Limit

High
Limit

32767 = 10V dc – 1 LSB

(input max.)

Process operating range

500

°

C

100

°

C

300

°

C

275

°

C

(Scaled max.)

(Scaled min.)

Input Value