Festo — CPX-4AE-4AA-H — 2021-06b
Commissioning
41
Digital input value = (actual value - 4) x 27648 / 16
Actual value
Digital input value
Meaning
> 22.81 mA
32767
Overflow
22.81 mA
32511
End of the measuring range
Ü
20 mA
27649 … 32511
Overdrive range
4 … 20 mA
0 … 27648
Nominal range
< 4 mA
-1 … -4864
Underdrive range
1.19 mA
-4864
End of the measuring range
Tab. 35: Range of values for fixed data format (input 4 … 20 mA)
7.5.3
Input 4 … 20 mA - scalable data format
–
Measuring range 4 … 20 mA
–
Scalable data format -32768 … 0 … 32767
–
Scaling above the lower and upper critical limit
–
Use of the critical limits for diagnostics
–
Conversion of the current values 1.19 … 22.81 mA (for sufficiently scaled data range)
–
Overflow or underflow for values outside of the data range for actual values (> 22.81 mA or
< 1.19 mA) or digital input value (> 32767 or < -32768)
–
Conversion of analogue actual value to the digital input value:
Digital input value = (actual value - 4) x (upper critical limit - lower critical limit) / 16 + lower critical
limit
To perform complete diagnostics: do not scale the measuring range above the complete data range.
Actual value
Digital input value
Meaning
4 … 20 mA
-32768 … 32767
Nominal range, freely scalable
< 1.19 mA
-32768
Underflow
Tab. 36: Range of values for scalable data format (input 4 … 20 mA)
7.5.4
Input 0 … 20 mA - fixed data format
–
Measuring range 0 … 20 mA
–
Data format not scalable
–
No underflow: actual values < 0 mA not possible (reverse polarity protection)
–
Conversion of analogue actual value to the digital input value:
Digital input value = actual value x 27648 / 20
Actual value
Digital input value
Meaning
23.52 mA
32511
End of the measuring range
> 20 mA
27649 … 32511
Overdrive range
