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Forum » Siemens » Help » Would some one please tell me, why Analog count is 27648?
Would some one please tell me, why Analog count is 27648?
CASPERDate: Tuesday, 2008-08-12, 7:56 AM | Message # 1
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Would some one please tell me, why Analog count is 27648?

In S7, the analog value (only <16 bit resolution) is represented left justified. i.e: 15th bit is sign and irrespective of you resolution of the ADC, the count remains same except the least significant bits

Resolution
Analog value

Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0

16-bit analog value
0
1
0
0
0
1
1
0
0
1
1
1
0
0
1
1

13-bit analog value
0
1
0
0
0
1
1
0
0
1
1
1
0
0
0
0

Here you can see that for 13 bit value, the LSBs are just set to zero. By doing this all resolution cards give same RAW value range.

Now, For analog value, you need to have undeshoot, and over shoot ranges. The table below may make it is easy to understand. Look at the Hex numbers, it is kind of understandable how they arrived at the 'magical number' of 27648 smile

dec hex ±20 mA
32767 7FFF 23.70 mA Overflow
32512 7F00
32511 7EFF 23.52 mA Overshoot range
27649 6C01
27648 6C00 20 mA Rated range
20736 5100 15 mA
1 1 723.4 nA
0 0 0 mA
-1 FFFF
-20736 AF00 -15 mA
-27648 9400 -20 mA
-27649 93FF Undershoot range
-32512 8100 -23.52 mA
-32513 80FF Underflow
-32768 8000 -23.70 mA

Hope this maked it clear.
You have many Part.

This are all Analog Inputs

0..20mA
0...5Volt
0...10Volt
0...400Ohm
PT100 Sensor (100hm 20°C)
PT1000 Sensors (1000Ohm 20°C)
NiCrNi THermoelemente

Wich number shold by an 10Volt or 5 Volt ?

and so on.

And all Units have as Example 27648 is 100% from all Units (Normaly)

0...5Volt 100% 27648
0..10Volt 100% 27648

I hove that ist the answer for your question.

 
Forum » Siemens » Help » Would some one please tell me, why Analog count is 27648?
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