Redundant use
In redundant mode, the modules AI 8 x 16 Bit are present in duplicate and are configured and
operated redundantly.
● If in redundant mode the substitute value behavior of the current outputs is set to "has no
current or voltage", in STOP state of the CPU or when the Profibus connection fails, a
current of approximately 115 μA is nevertheless output at each channel.
● Redundancy is only possible in 4-wire transducer operation of the module. Configuration as
a 4-wire transducer in HW-Config is required (see figure showing connection of 2-wire
transducer). Terminals 10 and 11 on the front panel connector must not be connected.
● In redundant mode, the voltage drop on both modules must be observed. To ensure a
sufficient voltage supply for the transducer, the voltage drop on both modules and the
voltage drop on the wiring and on the transducer must be observed (series connection).
With a sensor current of 22 mA, a voltage drop of approximately 3.3 V occurs on each
module. If you are using the protection circuit with Zener diodes shown below and you
replace the modules, note that the voltage drop on the removed module is the Zener voltage
(5.1 V) and the voltage drop on the inserted module continues to be 3.3 V.
ET 200PA SMART I/O modules
10.4 Analog input modules
ET 200PA SMART
168 Operating Instructions, 06/2019, A5E34192013-AB
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