User Manual

Publication 1746-UM003A-EN-P
4-12 Channel Configuration, Data, and Status
Proportional Counts to Engineering Units
Equation:
Assume that input type is a potentiometer (1000
Ω, range = 0 to 1000Ω),
proportional counts display type. Channel data = 21567.
Want to calculate ohms equivalent.
From Channel Data Word Format, S
LOW
= 0Ω and S
HIGH
= 1000Ω.
Solution:
Engineering Units to Proportional Counts
Equation:
Assume that input type is a potentiometer (3000
Ω, range = 0 to 3000Ω),
proportional counts display type. Desired channel resistance value = 1809
Ω.
Want to calculate Proportional Counts equivalent.
From Channel Data Word Format, S
LOW
= 0Ω and S
HIGH
= 3000Ω.
Solution:
The following table shows the temperature ranges of several 1746-NR8 RTDs.
The table applies to both 0.25 and 1.0 mA excitation currents. The
temperature ranges of the remaining RTDs vary with excitation current, for
example, 1000
Ω Platinum 385, 1000Ω Platinum 3916, and 10Ω Copper 426.
Engr Units Equivalent SLOW SHIGH - SLOW()
Proportional Counts value displayed + 32768()
65536
-------------------------------------------------------------------------------------------------------------------------
×



+=
Engr Units Equivalent 0 Ω 1000 ohms - 0 ohms[]
21567 32768+()
65536
------- -------------------------------------
×



826 ohms=+=
Proportional Counts Equivalent 65536
Engr Units desired - SLOW
()
SHIGH - SLOW()
------- ----------------------------- --------------- -----------------------
×



- 32768=
Prop. Counts = {65536 x [1809 ohms - 0 ohms]} -32768 = 6750