Scaling examples, Scaling examples -7 – Rockwell Automation 1746-NT8 SLC 500 Thermocouple/mV Analog Input Module User Manual User Manual
Page 47
Publication 1746-UM022B-EN-P - January 2005
Channel Configuration, Data, and Status 4-7
Scaling Examples
Scaled-for-PID to Engineering Units
Equation:
Engineering Units Equivalent = S
LOW
+ [(S
HIGH
-S
LOW
) x (Scaled-for-PID value displayed/16384)]
Data:
Assume type J input type, scaled-for-PID display type, channel data = 3421.
Want to calculate °C equivalent.
From Channel Data Word Format table, S
LOW
= -210°C and S
HIGH
= 760°C.
Solution:
Engineering Units Equivalent = -210°C + [(760°C-(-210°C)) x (3421/16384)] = -7.46°C.
Engineering Units to Scaled-for-PID
Equation:
Scaled-for-PID Equivalent = 16384 x [(Engineering Units desired -S
LOW
)/(SHIGH-S
LOW
)]
Data:
Assume type J input type, scaled-for-PID display type, desired channel temp. = 344°C.
Want to calculate Scaled-for-PID equivalent.
From Channel Data Word Format table, S
LOW
= -210°C and S
HIGH
= 760
°C.
Solution:
Scaled-for-PID Equivalent = 16384 x [(344°C - (-210°C))/(760°C - (-210°C))] = 9357
Proportional Counts to Engineering Units
Equation:
Engineering Units Equivalent = S
LOW
+ {(S
HIGH
-S
LOW
) x [(Proportional Counts value displayed +
32768)/ 65536]}
Data:
Assume type E input type, proportional counts display type, channel data = 21567.
Want to calculate °F equivalent.
From Channel Data Word Format table, S
LOW
= -454°F and S
HIGH
=1832°F
Solution:
Engineering Units Equivalent = -454°F + {[1832°F -(-454°F)] x [(21567 + 32768)/65536]} = 1441.3°F
Engineering Units to Proportional Counts
Equation:
Proportional Counts Equivalent = {65536 x[(Engineering Units desired - S
LOW
)/(S
HIGH
-S
LOW
)]} -32768
Data:
Assume type E input type, proportional counts display type, desired channel temp. = 1000°F.
Want to calculate Proportional Counts equivalent.
From Channel Data Word Format table, SLOW = -454°F and SHIGH = 1832°F.
Proportional Counts Equivalent = {65536 x[100°F - (-454°F)/(1832°F - (-454°F)]} - 32768 = 8916.
Solution:
Proportional Counts Equivalent = {65536 x[1000°F - (-454°F)/(1832°F - (-454°F)]} - 32768 = 8916.