6/20/2010 2:55 PM | |
Joined: 7/2/2008 Last visit: 8/26/2024 Posts: 928 Rating:
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Hello d.barnabe,
Unfortunately there's still a bit of debate till the day we are living. Some old guys say that it's always better and easier to trace a fault in 4-20mA system while it's hard to do it quickly in a Fieldbus system. I do like 4-20mA but I like Fieldbus more. It just needs appropriate knowledge and maybe a bit of training then it's easier and more comfort than the huge number of 4-20mA wires and their marshaling cabinets and termination diagrams. Profibus has two main variants, DP (Decentralized Peripherals) which is mainly based on RS485 and can go up to 12MB/S. It's mainly used in factory automation since it can go faster than most of other industrial communication busses. PA (Process Automation) which has a different physical layer (MBP) that's limited to31.25 KB/s (which is enough for process automation). The main advantage of this physical layer is that it can power all instruments (that used to be loop powered) through the same communication bus. HART (Highway Addressable Remote Transducer) is quite an old technology that was amazing at its time (1.2KB/S). Although some vendors still fight the high waves of Fieldbus technology depending on the large installed base of HART and although the HART is proving itself nowadays in wireless transmitters, I still believe that HART will not be able to resist Fieldbus technology in the coming few years. I have just found this document that talks about differences between HART and FF (Foundation Fieldbus) and why to use FF instead of HART. The FF is quite similar to Profibus PA. So you can just replace FF with Profibus PA in this document. For me I would say PROFIBUS is easier but I'm not sure it's cheaper. However I'm sure it's capable of doing the 2nd part better than HART. Yes for sure. I'm not sure because verificators perform tests on flow meters anddefinitely some of its result data come from performed tests and maybe such data won't be available in the transmitter itself. So, what kind of data do you wish to have? If this's all about magnetic flowmeters then PROFIBUS DP would be enough because in all cases magnetic flow meters are powered separately. At this point, HART might be more expensive but it needs to be calculated since you will have to add PROFIBUS DP modules to magnetic flow meters. No. It's called HART over PROFIBUS which means that HART data records are transferred through PROFIBUS (ET200M). I believe you will find all what you are looking for in, SIMATIC ET 200M distributed I/O device HART analog modules To be able to easily read diagnostics from either PROFIBUS instruments or HART instruments, you will need SIMATIC PDM. You can find more about SIMATIC PDM here Best regards. H-H |
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