Siemens SIMATIC S7-400H - Page 192

Using I/Os in S7–400H
13.4 Connecting redundant I/O to the PROFIBUS DP interface
S7-400H
192 System Manual, 03/2012, A5E00267695-11
Library V5.x Library V4.x Library V3.x Module Order number
AI 8x16Bit 6ES7 331–7NF00–0AB0
X X X
Use in voltage measurement
 The "wire break" diagnostics function in HW Config must not be activated
when operating the modules with transmitters.
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 10-9.
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 scenario: 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 overshoot value
24 mA to U
e-2w
= R
E
* I
max
+ U
z max
)
AI 8x16Bit 6ES7 331–7NF10–0AB0 X X
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 in indirect current measurement
 Use a 250 ohm resistor (measuring range 1 - 5 V) to map the current on a
voltage; see figure 10-9.
Use in direct current measurement
 Suitable Zener diode: BZX85C8v2
 Load capability of 4-wire transmitters: R
B
> 610 ohms
(determined for worst case scenario: 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
overshoot value 24 mA to U
e-2w
= R
E
* I
max
+ U
z max
)