Rockwell Automation AB quality Allen-Bradley 1746-INT4 User Manual page 49

Convert from Scaled-for-PID to Equivalent Engineering Units in °C
Equation: Engr Units Equivalent =
Solution: Engr Units Equivalent =
Convert from Engineering Units in °C to Equivalent Scaled-for-PID Count
Equation: Scaled-for-PID Equivalent =
Solution: Scaled-for-PID Equivalent =
Convert from Proportional Counts to Equivalent Engineering Units in °F
Equation: Engr Units Equivalent =
Solution: Engr Units Equivalent =
Convert from Engineering Units in °F to Equivalent Proportional Counts
Equation: Proportional Counts Equivalent = {65,536 x [(Engineering Units desired – S
Solution: Proportional Counts Equivalent = {65,536 x [(1000 °F – (-454 °F)) / (1832 °F – (-454 °F))]} – 32,768 = 8916 counts.
Select the Correct Data Format
To provide the highest display resolution, select Scaled-for-PID or
Proportional Counts. To use either one, you may have to convert
channel data to/from Engineering Units, manually or logically.
The following examples show you how to do this.
Use Scaled-for-PID and Proportional Counts
You must obtain the minimum (S
of the temperature or millivolt range for the channel's input type, and
use them in your computations.
We present these values in the section Using Channel Data Words on
page 51, in the table Format of a Channel Data Word.
Scaling Examples: Convert Between Units
S + [(S – S ) x (Scaled-for-PID value displayed / 16,384)]
LOW HIGH LOW
Assume type J input type, scaled-for-PID, channel data = 3421.
From Channel Data Word Format table, S
-210 °C + [(760 °C – (-210 °C)) x (3421 / 16,384)] = -7.46 °C
16,384 x [(Engineering Units desired – S
Assume type J input type, scaled-for-PID, desired channel temp. = 344 °C.
From Channel Data Word Format table, S
16,384 x [(344 °C – (-210 °C)) / (760 °C – (-210 °C))] = 9357.
S + [(S – S ) x [(Proportional Counts value displayed + 32,768) / 65,536]]
LOW HIGH LOW
Assume type E input type, proportional counts, channel data = 21,567 counts.
From Channel Data Word Format table, S
-454 °F + [[1832 °F – (-454 °F)] x [(21,567 + 32,768) / 65,536]] = 1441.3 °F
Assume type E input type, proportional counts, desired channel temp. = 1000 °F.
From Channel Data Word Format table, S
Channel Configuration, Data, and Status
) and maximum (S
LOW
= –210 °C and S = 760 °C.
LOW HIGH
) / (S – S ]
LOW HIGH LOW
= –210 °C and S = 760 °C.
LOW HIGH
= –454 °F and S = 1832 °F.
LOW HIGH
) / (S – S )]} – 32,768
LOW HIGH LOW
= -454 °F and S = 1832 °F.
LOW HIGH
Publication 1746-UM614B-EN-P - September 2007
49
) values
HIGH