Rockwell Automation 1746-NI8 SLC 500 Analog Input Modules User Manual - Manual (Page 50)

5–9 Channel Configuration, Data, and Status
Publication 1746Ć6.8 - April 1997
Scaled-for-PID to “Real” Units
Situation: A transducer is being used to measure temperature.
The 4–20 mA signal is proportional to 100–500
°
C (212–932
°
F).
The channel data word is in scaled-for-PID format.
The channel data = 5500.
Find: “Real” units equivalent in
°
F.
Equation:
Real Units Equivalent + S
LOW
)
ƪ
(S
HIGH
* S
LOW
)
ǒ
channel data value
full scale default PID value
Ǔ
ƫ
where: S
LOW
= 212
°
F
S
HIGH
= 932
°
F
channel data word = 5500
full scale PID default value (from table on page
5–6) = 16383
Solution:
RealăUnitsăEquivalent + 212°F )
ƪ
(932°F * 212°F)
ǒ
5500
16383
Ǔ ƫ
+ 453.71°F
Proportional Counts to “Real” Units
Situation: A transducer is being used to measure pressure.
The –10V dc to +10V dc signal is proportional to 0 to 200 psi.
The channel data word is in proportional counts data format.
The channel data = 21567.
Find: “Real” units equivalent in psi.
Equation:
Real Units Equivalent + S
LOW
)
ƪ
(S
HIGH
* S
LOW
)
ǒdata value ) Ť proportional count low default valueŤāǓ
ǒproportional count full scale default valueǓ
ƫ
where: S
LOW
= 0 psi
S
HIGH
= 200 psi
channel data = 21567
proportional count low default value (from table on page 5–6) = –32768
proportional count full scale default value (from table on page
5–6) = 65535
Solution:
Real Units Equivalent + 0 psi )
ƪ
ǒ200 psi * 0 psiǓ
ǒ21567 ) Ť -32678ŤāǓ
(65535)
ƫ
+ 165.55 psi