Using I/Os in S7–400H
13.4 Connecting redundant I/O to the PROFIBUS DP interface
S7-400H
200
System Manual, 03/2012, A5E00267695-11
Redundant analog input modules for indirect current measurement
The following applies to the wiring of analog input modules:
●
Suitable encoders for this circuit are active transmitters with voltage output and
thermocouples.
●
The "wire break" diagnostics function in HW Config must not be activated, neither when
operating the modules with transmitters nor when thermocouples are connected.
●
Suitable encoder types are active 4-wire and passive 2-wire transmitters with output
/-20 mA, 0...20 mA, and 4...20 mA. 2-wire transmitters are powered by an
external auxiliary voltage.
●
Criteria for the selection of resistance and input voltage range are the measurement
accuracy, number format, maximum resolution and possible diagnostics.
●
In addition to the options listed, other input resistance and voltage combinations
according to Ohm’s law are also possible. Note, however, that such combinations may
lead to loss of the number format, diagnostics function and resolution. The measurement
error also depends largely on the size of the measure resistance of certain modules.
●
Use a measure resistance with a tolerance of +/- 0.1% and TC 15 ppm.
Additional conditions for specific modules
AI 8x12bit 6ES7 331–7K..02–0AB0
●
Use a 50 ohm or 250 ohm resistor to map the current on a voltage:
Resistor
50 ohms
250 ohms
Current measuring range
+/-20 mA
+/-20 mA *)
4...20 mA
Input range to be parameterized
+/-1 V
+/-5 V
1...5 V
Measuring range cube position
"A"
"B"
Resolution
12 bits + sign
12 bits + sign
12 bits
S7 number format
x
x
Circuit-specific measuring error
- 2 parallel inputs
- 1 input
-
-
0.5%
0.25%
"Wire break" diagnostics
-
-
x *)
Load for 4-wire transmitters
50 ohms
250 ohms
Input voltage for 2-wire transmitters
> 1.2 V
> 6 V
*) The AI 8x12bit outputs diagnostic interrupt and measured value "7FFF" in the event of wire break.
The listed measuring error results solely from the interconnection of one or two voltage
inputs with a measure resistance. Allowance has neither been made here for the tolerance
nor for the basic/operational limits of the modules.
Содержание SIMATIC S7-400H
Страница 24: ...Preface 1 1 Preface S7 400H 24 System Manual 03 2012 A5E00267695 11 ...
Страница 46: ...Getting Started 4 5 Special layout features of SIMATIC Manager S7 400H 46 System Manual 03 2012 A5E00267695 11 ...
Страница 120: ...Memory concept 10 1 Overview of the memory concept of S7 400H CPUs S7 400H 120 System Manual 03 2012 A5E00267695 11 ...
Страница 258: ...Communication 14 8 General issues regarding communication S7 400H 258 System Manual 03 2012 A5E00267695 11 ...
Страница 354: ...Synchronization modules 18 3 Selecting fiber optic cables S7 400H 354 System Manual 03 2012 A5E00267695 11 ...
Страница 434: ...Technical data 20 6 Runtimes of the FCs and FBs for redundant I Os S7 400H 434 System Manual 03 2012 A5E00267695 11 ...
Страница 460: ...Function modules and communication processors supported by the S7 400H S7 400H 460 System Manual 03 2012 A5E00267695 11 ...