Analog Value Representation For Measuring Ranges With Simatic S7 - Siemens SIMATIC ET 200S Manual

Analog Electronic Modules
12.1.1 Analog Value Representation for measuring ranges with
SIMATIC S7
Analog value visualization
With the same nominal range, the digitized analog value is the same for input and
output values. Analog values are represented in two's complement.
The following table shows the analog value representation of the analog
electronics modules.
Table 12-2 Analog Value Representation (SIMATIC S7 Format)
Resolution
Bit number
Significance of the bits
Sign
The sign (S) of the analog value is always in bit number 15:
• "0" → +
• "1" → −
Measured Value Resolution
The following table shows the representation of the binary analog values and the
corresponding decimal and hexadecimal representation of the units of the analog
values.
The table12-3 shows the resolutions 11, 12, 13, and 15 bit + sign are shown. Each
analog value is entered left aligned in the ACCU. The bits marked with "x" are set
to "0".
Table 12-3 Measured Value Resolution of the Analog Values (SIMATIC S7 Format)
Resolution in Bits
11+S
12+S
13+S
15+S
Note: This resolution does not apply for temperature values. The converted
temperature values are the result of a conversion in the analog electronics module
(see table 12-3).
12-4
15 14 13 12 11
14 13 12 11
S 2 2 2 2
Units
decimal hexadeci-
mal
16 10
H
8 8
H
4 4
H
1 1
H
Analog Value
10 9 8 7 6
10 9 8 7 6
2 2 2 2 2
Analog Value
high byte
S 0 0 0 0 0 0 0
S 0 0 0 0 0 0 0
S 0 0 0 0 0 0 0
S 0 0 0 0 0 0 0
5 4 3 2 1
5 4 3 2 1
2 2 2 2 2
low byte
0 0 0 1 x x x x
0 0 0 0 1 x x x
0 0 0 0 0 1 x x
0 0 0 0 0 0 0 1
ET 200S Distributed I/O System
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