Rockwell Automation 1762-IR4 RTD/Resistance Input Module - Manual (Page 46)

Publication 1762-UM003A-EN-P - February 2003
3-12 Module Data, Status, and Channel Configuration
EXAMPLE
Engineering Units x1 to Scaled-for-PID
•
input type = 200
Ω
Platinum RTD
• α
= 0.00385°C
•
range = -200 to +850°C S
LOW
= -200°C S
HIGH
= +850°C
•
desired channel temperature = 344°C (engineering units)
Scaled-for-PID Equivalent = 16383 x [(desired ch. temp. - S
LOW
)/(S
HIGH
- S
LOW
)]
Scaled-for-PID Equivalent = 16383 x [(344°C - (-200°C))/(850°C - (-200°C))] = 8488
EXAMPLE
Proportional Counts to Engineering Units x1
•
input type = 1000
Ω
potentiometer
•
range = 0 to 1000
Ω
S
LOW
= 0
Ω
S
HIGH
= 1000
Ω
•
channel data = 21567 (proportional counts)
Engineering Units Equivalent =
S
LOW
+ {(S
HIGH
- S
LOW
) x [(ch. data + 32768)/65536]}
Engineering Units Equivalent =
0 + {(1000 - 0) x [(21567 + 32768)/65536]} = 829
Ω
EXAMPLE
Engineering Units x1 to Proportional Counts
•
input type = 3000
Ω
potentiometer
•
range = 0 to 3000
Ω
S
LOW
= 0
Ω
S
HIGH
= 3000
Ω
•
desired channel resistance = 1809
Ω
(engineering units x 1)
Prop. Counts Equivalent =
{65536 x [(ch. resistance - S
LOW
)/(S
HIGH
- S
LOW
)]} - 32768
Proportional Counts Equivalent =
{65536 x [(1809
Ω
-
0) / (3000 − 0) ] } − 32768
= 6750