craig anstee

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hi im interested in knowing the answers to these questions.

1)what is a profibus system
2)how a plc converts its output signal from digital to analogue.

any help with these questions would be much appretiated.
 
a profibus system is one of he ways for sending and recieving data from and to the PLC. the advantage of this is that you wont have to use a large amount of cables in a machine but just a profibus cable to a slave.

the digital signal comes out of an analog output as a certain voltage (i believe 0-10V) the times i used this voltage it stoud for the number 27550. but this is explained at "learn PLC's" on the top of this page

regards walters
 
I have the same problem in understanding the new technology. I'm not saying that I am an expert now, just awareness I must say.

Anyway, you may want to start with fieldbus. Search it in the internet. Then you may want to focus on one by one of the fieldbuses... like Foundation fieldbus, profibus, devicenet, AS-i, HART, etc...

I myself find it very hard to explain, as I just attended a seminar on Profibus they held here in my country (best way to find out). YOu may come across the term Profibus, Profibus DP, Profibus PA, Profibus FMS, Profinet, Profisafe....

Just an idea.....
 
Digital to analog conversion is essentially the opposite process from an analog input.

The CPU sends a specific data value to the analog output card. There special purpose processors convert the data to an electrical voltage signal that is proportional to the data. The value of data that represents 100% output signal depends on the specific card. For a 12 bit analog output 4095 represents 100%. For a 16 bit analog card 65536 may represent 100% output. Each manufacturer and modle of card tends to have their own range. Then an op-amp (operational amplifier) boosts this low level voltage to a higher level, say 0-10VDC or 4-20 mA.
 
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