FF vs. PA

[j.sarapaa]

hello!

I'd like to know what are THE main differences between FF and profibus PA technologies. How do I know which one to choose`?

also

-what advantages I get from FF's versatile function block, when PA's function block only includes AI/AO and DI/DO?

-what is user layer in FF

-Can I add traditional field devices to fieldbus bus (in FF and PA)

-is it possible add/remove devices while bus is active (in FF and PA)

-what are the main benefits when using fieldbus instead of traditional analog technolofy?

-they say that design work is more easier when using fielbus techolgy, why is that

-how is it possible that both FF and PA are THE leading fieldbus technologies in the world?

thanks
j.sarapaa

[jberge]

First, PA is the field-level version of Profibus corresponding to FF H1. FF also includes HSE corresponding to Profibus-DP and PROFInet at the host-level of the system architecture. A full comparison should really look at the complete architectures.

It is not so easy to compare Fieldbus with Profibus although PA happens to use the same media as H1. Profibus is more similar to Modbus so it would be easier to compare against that.

The at the data link level the basic difference is that Profibus only support poll-response type communication for cyclic and acyclic read and write. FF is more sophisticated also supporting modern communication schemes such as scheduled publisher/subscriber and report distribution. Profibus is only master-slave, whereas FF supports peer-to-peer communication. At the application layer and in the user application these functions are then used to achieve benefits such as diagnostic events and alarms etc. that Profibus cannot do, as well as links between decentralized function blocks.

Profibus has several schemes for host interoperability: Profile, EDDL, and FDT/DTM (note that GSD is NOT like DD, it provides no interoperability for device parameterization). None of them are really dominant. FF only has DD. In this case more is not merrier because the device you want to connect may not have supporting EDDL files, and the host you have may not support DTM. The device may not correspond to a particular profile either. I.e. there can be situations where you cannot fully tap the potential of the device. FF has no such problem because there is only DD. All devices have DD, all hosts support DD.

I have a lengthy comparison I can send you if you like. Contact me directly at jberge@smar.com.sg

See also chapter 2 in the book "Fieldbuses for Process Control: Engineering, Operation, and Maintenance" (buy online in hardcopy or download immediately in softcopy):
http://www.isa.org/fieldbuses
If you can't buy the book now, you can download chapter 1 (overview) for free in softcopy form. It's free, but you must register an account. If your email does not support this hyperlink feature correctly, please copy the entire link and paste it into your Internet browser. Mind the line wrap, make sure to get the complete path all the way to the 4585:
http://www.isa.org/Template.cfm?Section=Shop_ISA&template=/Ecommerce/ProductDisplay.cfm&ProductID=4585

With FF blocks you can do decentralized control. It reduces the need for CPU cards in centralized controllers. It provides better safety and availability. Ultimately it reduces costs and risk. The blocks is a standard programming language for building control strategies, that in some systems completely takes the place of proprietary programming languages - and standard are good. See chapter 1, 2, and 10 in the above mentioned book

'User layer' is a popular name for what should really be called 'user application'. It really refers to the function blocks. DP/PA usually say that they have no application layer or user application, but the PA profile really is the equivalent. See chapter 11 in the above mentioned book.


We (SMAR) make converters for connecting 4-20 mA devices on H1 or PA. IF302 has 4-20 mA input, and FI302 has 4-20 mA output. The equivalent PA versions are called IF303 and FI303.

Advantages include more diagnostics, and less wiring - in that order. See chapter 2 of the above mentioned book for a full discussion

Some are able to make Fieldbus engineering more complicated :-). But really, because you multidrop you have less wiring and therefore less documentation. The control strategy and field instruments are configured in the same tool (rather than separate workstation and handheld) ensuring that ranges in transmitters match the ranges in the controls, alarms and displays etc. You need less cross-referencing etc. All instrument information is in a single database. Instrument lists can be generated from the system configuration. Since devices are interoperable you can select instruments independent of the control system so you don’t have to fret over the difficult choice between a good system or good devices. At bidding stage you need not define detail characteristics of each desired block, simply be saying "standard FF PID" are you ensured that you get a PID that does everything you ever wanted for basically every PID loop.

H1, PA, and HART are all fieldbuses, but surely there can only be one which is number one? I think a good measure of leadership for a bus technology is how many hosts that support them FULLY. By fully I mean not just an interface card, but ability to interpret the device support files to provide device parameterization. Users may want to check:
- How many hosts support HART DD
- How many hosts support FF DD
- How many hosts support Profibus DD and FDT/DTM

[JuanCarlos]

From Peru ; I want to know about Profibus PA

Hi Jonas ; I was looking for information about Profibus PA , I found http://www.fieldbus.org , in this web page there is a Forum , there I found what you help to someone . I hope you help me with the following questions:

1. How many types protocol Profibus there are?
2. What is Profibus PA and how does it work?

I will appreciate you help me.

Bye

Juan Carlos Vásquez
Techvalue Peru SAC
Sales Engineer - Industrial Networking
Gomez del Carpio 160
Surquillo - Peru
Telf: (511) 243-3881
Fax: (511) 243-3887
Celular: (511) 975-57402
E-mail: jc.vasquez@techvalue.com.pe (jc.vasquez@techvalue.com.pe)
Web: www.techvalue.com.pe

[Stephen Mitschke]

Hello Juan,

This forum is primarily related to topics on Foundation Fieldbus. I do suspect that some members such as Jonas will also have experience with other industrial protocols such as Profibus.

I would recommend that you visit sites such as http://www.profibus.com for answers specific to Profibus PA.

Good Luck,
Stephen




From Peru ; I want to know about Profibus PA

Hi Jonas ; I was looking for information about Profibus PA , I found http://www.fieldbus.org , in this web page there is a Forum , there I found what you help to someone . I hope you help me with the following questions:

1. How many types protocol Profibus there are?
2. What is Profibus PA and how does it work?

I will appreciate you help me.

Bye

Juan Carlos Vásquez
Techvalue Peru SAC
Sales Engineer - Industrial Networking
Gomez del Carpio 160
Surquillo - Peru
Telf: (511) 243-3881
Fax: (511) 243-3887
Celular: (511) 975-57402
E-mail: jc.vasquez@techvalue.com.pe (jc.vasquez@techvalue.com.pe)
Web: www.techvalue.com.pe (http://www.techvalue.com.pe)