I/O configuration variants
4.7 Connecting redundant I/O to the PROFIBUS DP interface
CPU 410-5H Process Automation
78 System Manual, 09/2014, A5E31622160-AB
• The equipotential bonding of the load circuit should always take place from one point only (preferably load minus).
DO 10xDC 24 V/2 A 6ES7326–2BF00–0AB0
F-module in standard mode
Redundant AI dual-channel
Use in voltage measurement
• The "wire break" diagnostics function in HW Config must not be activated, neither when operating the modules with
transmitters nor when thermocouples are connected.
Use for indirect current measurement
• When determining the measuring error, observe the following: The total input resistance in measuring ranges > 2.5 V is
reduced from a nominal 100 kilohm to 50 kilohm when operating two inputs connected in parallel.
• The "wire break" diagnostics function in HW Config must not be activated, neither when operating the modules with
transmitters nor when thermocouples are connected.
• Use a 50 ohm resistor (measuring range +/- 1 V) or 250 ohm resistor (measuring range 1 - 5 V) to map the current on a
voltage, see figure 11-4. The tolerance of the resistor must be added on to the module error.
• This module is not suitable for direct current measurement.
Use of redundant encoders:
• You can use a redundant encoder with the following voltage settings:
+/- 80 mV (only without wire break monitoring)
+/- 250 mV (only without wire break monitoring)
+/- 500 mV (wire break monitoring not configurable)
+/- 1 V (wire break monitoring not configurable)
+/- 2.5 V (wire break monitoring not configurable)
+/- 5 V (wire break monitoring not configurable)
+/- 10 V (wire break monitoring not configurable)
1...5 V (wire break monitoring not configurable)
Use in voltage measurement
• The "wire break" diagnostics function in HW Config must not be activated when operating the modules with transmit-
ters.
Use in indirect current measurement
• When using indirect current measurement, ensure a reliable connection between the sensor resistances and the actual
inputs, because a reliable wire break detection cannot be guaranteed in the case of a wire break of individual cables of
this connection.
• Use a 250 ohm resistor (measuring range 1 - 5 V) to map the current on a voltage; see figure 11-4.
Use in direct current measurement
• Suitable Zener diode: BZX85C8v2
• Circuit-specific additional error: If one module fails, the other may suddenly show an additional error of approx. 0.1%.
• Load capability of 4-wire transmitters: R
B
> 610 ohms
(determined for worst case: 1 input + 1 Zener diode at an S7 overload value 24 mA to R
B
= (R
E
* I
max
+ U
z max
)/I
max)
• Input voltage in the circuit when operating with a 2-wire transmitter: U
e-2w
< 15 V
(determined for worst case: 1 input + 1 Zener diode at an S7 overload value 24 mA to U
e-2w
= R
E
* I
max
+ U
z max
)