Siemens SIMATIC S7-400H Manual page 159

Additional marginal conditions for various modules
AI 8x16bit
• Suitable Z diodes: BZX85C8v2 or 1N4738A (8.2 V because of 250 Ohm input
resistance)
• Cumulative circuit error: When one of the modules fails, the error value of the
other may increase instantaneously by approx. 0.1%
• Load capability of 4-wire measurement transducers: R
calculation: 1 input + 1 Zener diode with an S7 saturation value of 24 mA; R
(R * I
E max
• Input voltage of 2-wire measurement transducers: U
calculation: 1 input + 1 Zener diode with an S7 saturation value of 24 mA;
U
in–2Dr
AI 16x16bit
• Suitable Z diodes BZX85C6v2 or 1N4734A (6.2 V because of 50 Ohm input
resistance)
• Cumulative circuit error: ––
• Load capability of 4-wire measurement transducers: R
calculation: 1 input + 1 Zener diode with an S7 saturation value of 24 mA; R
(R * I
E max
• Input voltage of 2-wire measurement transducers: Uin
calculation: 1 input + 1 Zener diode with an S7 saturation value of 24 mA;
U
in–2Dr
Note
The circuit shown above operates only with active 4-wire measurement
transducers, or with passive 2-wire measurement transducers connected to an
auxiliary load voltage supply. The module channels always have to configured for
"4-wire measurement transducer" operation.
The module (2DMU) can not supply the MT voltage.
AI 4x15bit Ex
• Note the relevant specifications when operating the module in Ex areas.
• Suitable Zener diodes: BZX85C6v2 or 1N4734A (6.2 V because of 50 Ohm
input resistance)
• Cumulative circuit error: ––
• Load capability of 4-wire measurement transducers: RB > 325 Ohm (worst case
calculation: 1 input + 1 Zener diode with an S7 saturation value of 24 mA; R
(R * I
E
• Input voltage of 2-wire measurement transducers: Uin-2Dr < 8 V (worst case
calculation: 1 input + 1 Zener diode with an S7 saturation value of 24 mA;
Uin-2Dr = R
Automation System S7-400H Fault-tolerant Systems
A5E00068197-07
+ U ) / I
)
z max max
= R * I + U )
z max
E max
+ U ) / I
)
z max max
= R * I + U )
E max z max
U ) / I
+ )
max z max max
* I + U
)
E
max z max
6ES7 331-7NF00-0AB0
6ES7 431-7QH00-0AB0
6ES7 331-7RD00-0AB0
Using I/O on the S7-400H
> 610 Ohm (worst case
B
< 15 V (worst case
in–2Dr
> 325 Ohm (worst case
B
< 8 V (worst case
–2Dr
=
B
=
B
=
B
7-29