3 Product Description F3 AIO 8/4 01
Page 16 of 54 HI 800 161 E Rev. 1.01
The current through the Z-diode should be limited to 20 mA (specification of the Z-diode).
This results in a minimum value for the series resistor of:
R
diode
= 14.8 V / 20 mA = 740 Ω
The value for R
diode
can be set to 1 KΩ.
This resistance limits the maximum current through the Z-diode to approximately 15 mA.
A short-circuit within the red-colored area (see circuit diagram) can be monitored through
the voltage drop on the shunt R
shunt
, i.e., the input value of AI, see Table 7.
To allow line monitoring, the value of AI must be evaluated in the logic of the user program.
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