Owner's manual

56 Rockwell Automation Publication 1769-UM005B-EN-P - March 2012
Chapter 4 Module Data, Status, and Channel Configuration
Scaling Examples
EXAMPLE
Scaled-for-PID to Engineering Units x1
· input type = 200 Ω Platinum RTD
· α = 0.00385 °C
· range = -200…850 °C S
LOW
= -200 °C S
HIGH
= 850 °C
· channel data = 3421(scaled-for-PID)
Engineering Units Equivalent = S
LOW
+ [S
HIGH
- S
LOW
) x (channel data/16383)]
Engineering Units Equivalent = -200 °C + [(850 °C -(-200 °C)) x (3421/16383)] = 19.25 °C
EXAMPLE
Engineering Units x1 to Scaled-for-PID
· input type = 200 Ω Platinum RTD
· α = 0.00385 °C
· range = -200…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…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]} = 829Ω
EXAMPLE
Engineering Units x1 to Proportional Counts
· input type = 3000 Ω potentiometer
· range = 0…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