Rockwell Automation 1769-IR6 Compact I/O 1769-IR6 RTD/Resistance Input Module - Manual (Page 56)

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]} = 829
Ω
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