analog to digital conversions

gh_ounie

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• Oct 17, 2008

• #1

When I'm working in Step 7 with analog to digital conversions when i encounter a 12 bit i usually div on 27846 but really I don't know where this number comes from ?

 

seppoalanen

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• Oct 17, 2008

• #2

It is analog channel property. How analog unit scales electrical value to digital value.

S7-300 and M7-300
Programmable Controllers
Module specifications
Reference Manual.

Usually they are from 0 to 27846 or from -27846 to 27846 when mA or voltage signal have used.
It can be very different also, fe. with RTD (PT100) inputs.
Scaling to engineerin units, see:
http://www.plctalk.net/qanda/showthread.php?t=19159

 

Nick B

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• Oct 18, 2008

• #3

The number is the SAME regardless of resolution. The card brings back 16bit number less some overshoot. One of Siemens better features. You don't have to factor what your card resolution is. Look at FC105 and the I/O card manual for details.

Nick

 

krk

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• Oct 18, 2008

• #4

27648

 

benji

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• Oct 18, 2008

• #5

Why would you need to divide by 27648 ?
the range would be then from 0 to 1 ,right?

here is an example of using FC105 ,thanks to Madman

 

benji

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• Oct 18, 2008

• #6

http://www.plctalk.net/qanda/showthread.php?t=42272&page=2