42
Festo — CPX-4AE-4AA-H — 2021-06b
Commissioning
Actual value
Digital input value
Meaning
0 … 20 mA
0 … 27648
Nominal range
< 0 mA
–
Underflow not possible:
Reverse polarity protection
Tab. 37: Range of values for fixed data format (input 0 … 20 mA)
7.5.5
Input 0 … 20 mA - scalable data format
–
Measuring range 0 … 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 0 … 23.52 mA (for sufficiently scaled data range)
–
Overflow or underflow for values outside of the data range (> 32767 or < -32768)
–
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 (upper critical limit - lower critical limit) / 20 + lower critical limit
Actual value
Digital input
value
Meaning
> 23.52 mA (hysteresis < 23.42 mA)
32767
Overflow
0 … 20 mA
-32768 … 32767
Nominal range, freely scalable
< 0 mA
< -32768
Underflow not possible:
Reverse polarity protection
Tab. 38: Range of values for scalable data format (input 0 … 20 mA)
7.5.6
Output 4 … 20 mA - fixed data format
–
Value range 4 … 20 mA
–
Data format not scalable
–
Current value output 0 … 22 mA
–
Current value output in case of overflow (> 22 mA): 22 mA
–
Current value output in case of underflow (< 0 mA): 0 mA
–
Conversion of the digital output value to the analogue setpoint value (current value output)
Current value = 4 + 16 x digital output value / 27648
Digital output value
Current value output
Meaning
> 31104
22 mA
Overflow
31104
22 mA
End of output range
27649 … 31104
> 20 mA
Overdrive range
0 … 27648
4 … 20 mA
Nominal range
-1 … -6912
< 4 mA
Underdrive range
