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7.21.2
Analog value representation for measuring ranges with
SIMATIC S7
Analog value representation
The digitized analog value for input and output values in the same rated range is
the same.
The analog values are represented in the form of a twos complement.
The following table shows the analog value representation of the expansion
modules with analog inputs and outputs:
Table 7-43 Analog value representation (SIMATIC S7 format)
Resolution
Bit number
Significance of the bits
Sign
The sign (+/–) of the analog value is always in bit number 15:
S "0" ³ )
S "1" ³ *
Measured-value resolution
In the table below you will find the representation of the binary analog values and
the associated decimal and hexadecimal representation of the units of the analog
values.
The analog inputs have a resolution of 12 bits + plus/minus sign, whereas the
analog outputs have a resolution of 11 bits + plus/minus sign. Each analog value is
entered in the accumulator with left justification. The bits marked "x" are set to "0".
Note: This resolution does not apply to temperature values. The converted
temperature values are the result of a conversion in the expansion module (see
Table 7-47).
Table 7-44 Measured-value resolution of the analog values (SIMATIC S7 format)
Resolution in
Decimal
bits (plus +/–)
11
12
ET 200X Distributed I/O Device
EWA 4NEB 780601602-06
15
14
13
12
11
14
13
12
11
+/
2
2
2
2
–
Units
Hexadeci-
mal
16
10
H
8
8
H
Analog value
10
9
8
7
6
10
9
8
7
6
2
2
2
2
2
Analog value
High byte
+/– 0 0 0 0 0 0 0
+/– 0 0 0 0 0 0 0
Technical Specifications
5
4
3
2
1
0
5
4
3
2
1
2
2
2
2
2
2
Low byte
0 0 0 1 x x x x
0 0 0 0 1 x x x
7-87
0
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