Siemens SIMATIC S5-115U, User Manual

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S5-115U Manual Analog Value Processing
Differential Measurement
Figure 10-20. Pin Assignments of the 466 Analog Input Module in the Case of Differential
Measurement
Differential measurement is a method of
measuring which compensates for noise on
the line.
Each signal line is assigned its own signal refe-
rence line. By measuring the difference
between the signal line and the signal refe-
rence line, noise on both lines is compensated
for.
Unused channels also must be short-circuited
when using this method of measuring (jumper
between M+and M -).
Differential measurement is required in the
following cases:
•
When the sensors are connected to diffe-
rent supplies
• When different signal sources are physi-
cally separate
• When signals must be captured with high
accuracy
• When a high level of noise is expected.
Labelling and Grouping of Channels
The channels are labelled as follows on the
module:
M0 -
Channel 1: M1+
M1 -
: :
Channel 7: M7+
M7 -
The channels are arranged in groups of four,
for which separate measuring ranges can be
set:
Channel group I:
Group 0 to 3
Channel group II: Group 4 to 7
1
2
M0+
3 M ext
4 M ext
5 M0-
6
7
M1+
8 M ext
9 M ext
10 M1-
11
12
M2+
13 M ext
14 M ext
15 M2-
16
17
M3+
18 M ext
19 M ext
20 M3-
21
22
23
24
M4+
25 M ext
26 M ext
27 M4-
28
29
M5+
30 M ext
31 M ext
32 M5-
33
34
M6+
35 M ext
36 M ext
37 M6-
38
39
M7+
40 M ext
41 M ext
42 M7-
43
EWA 4NEB 811 6130-02b
10-31