Fieldbuses

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Thread Starter

arundhati

How do the various protocols like profibus, modbus, canbus, devicenet, data highways, etc compare? Which should one use for a new process control system?
 
J

James Ingraham

To answer your question with a personal opinion that's worth every penny you've paid for it:
If I were starting "a new process control system" today I would use Profibus. On the other hand, in the U.S. you are probably better off with Foundation Fieldbus. If your plant/customer has strong Allen-Bradley feelings, ControlNet would be a reasonable option.

The reality is that every project is different. Despite my Profibus favoritism, I would use something else in a heartbeat if their was a compelling reason. Reasons could be interopability with other equipment (including legacy equipment); a vendor that is very familiar with one particular fieldbus and can implement it quickly, easily, and cheaply; a product that would simplify the project that has only a limited number of possible networks; cost; speed; distance; impressing my boss; etc.

Bottom line is, if you are asking this question at this stage you are in trouble. You need to read up, and quickly.

Start with the fieldbus comparison chart at Lantronx / Synergetic. "www.synergetic.com/compare.htm":http://www.synergetic.com/compare.htm

You may also find Fieldbus World helpful.
"www.fieldbusworld.com":http://www.fieldbusworld.com

You might purchase the "Guide to the evaluation of fieldbus protocols" from The British Standards Institution (BSI), a 34-page document, doc# PD 0014:2000. It's aimed at end-users, and is intended to provide a basic understanding of fieldbus technology, as an aid to the selection of a suitable fieldbus for a particular application.
"www.romilly.co.uk/bsiguide.htm":http://www.romilly.co.uk/bsiguide.htm

Then look at individual fieldbus pages.

Profibus "www.profibus.com":http://www.profibus.com

Modbus "www.modbus.org":http://www.modbus.org

DeviceNet "www.odva.org":http://www.odva.org

AS-i "www.as-interface.com":http://www.as-interface.com

Foundation Fieldbus "www.fieldbus.org":http://www.fieldbus.org

HART "www.hartcomm.org":http://www.hartcomm.org

Interbus-S "www.interbusclub.com":http://www.interbusclub.com
LONWorks "www.echelon.com":http://www.echelon.com

WorldFIP "www.worldfip.org":http://www.worldfip.org

ControlNet "www.controlnet.org":http://www.controlnet.org

This is, of course, a partial list.

Good luck; you're gonna need it.

-James Ingraham
Sage Automation, Inc.
 
E
Some of the main differences include the speed of the network, how many drops are allowed, the length and of the bus, and ease of setup and debugging. For example Modbus is included on most manufacturers hardware and debugging just takes a simple serial port, but it is relatively slow. If you are asking youself which one to use for a new system, first consider which protocols are offered by the control system you are looking at and then write down specifics, like how many devices are going to be on the network, what is the total length, how much data and with how much speed do you need to update everything. Most of the time you will be limited by the hardware needed to meet your application and the other specifics listed above. One thing I would say is try to stick with the most widely use protocols for your field and/or reigon. It makes finding compatable hardware and finding help easier.
 
J
If you are doing process control then FOUNDATION(tm) is the most suitable. It has the support of most process control suppliers and has the broadest range of process instrumentation available, such as transmitter for flow, level, pressure, temperature, conductivity, pH, valve positioners and electrical actuators, controllers, on/off valve couplers, analyzers,
converters and recorders etc. System management ensures plug and play operation. Device description and an integrated programming language ensure interoperability. While a first generation system will only give you the
field-level H1 bus, a second generation system also has the HSE host-level bus rather than using proprietary control network.

See the below book. Chapter 2 contains all the reason why you should go FOUNDATION(tm) Fieldbus, which is also the material you need to justify the
project to your management.

"www.isa.org/Template.cfm?Section=Shop_ISA&Template=/Ecommerce/ProductDisplay.cfm&ProductID=3036":http://www.isa.org/Template.cfm?Sec...=/Ecommerce/ProductDisplay.cfm&ProductID=3036

You can download chapter 1 for free.

Jonas
 
G
I'm REALLY getting tired of this boasting nonsense and misinformation! Also, FF does NOT have the most support or broadest range of equipment! As enough qualified people have said, it's "horses for courses". Most all will work,
but all were designed for specific things. Where are you in the world? What sort of support structure is available? What are your integrators familiar with, etc. etc. Let's stop boasting whether Ford is better than Chevy (or whether Lexus is better than Infiniti).

Paul Gruhn, PE, CFSE
Siemens, Houston, TX
[email protected]
 
J
I did not say FF has the broadest range of equipment of any bus, I specifically said that FF has most products for "process instrumentation".
If you look at the list of registered products
( "http://www.fieldbus.org/ProductsAndServices/RegisteredProducts/":http://www.fieldbus.org/ProductsAndServices/RegisteredProducts/ ) I am sure
that you will not find a similar selection of transmitters for flow, level, pressure, temperature, conductivity, pH, valve positioners and electrical actuators, controllers, on/off valve couplers, analyzers, converters and
recorders etc. based on any other protocol (at least not purely digital). This is not misinformation.

Like you said, protocols are designed for specific things. Arundhati asked about process control, which is what FF was designed for. For another task some other protocol may work better.

I'm based in Singapore where many of the FF members have their regional head quarters. FF has also established an end-user council and a committee for manufacturers so the regional support structure for FF is pretty good.

Jonas Berge::

==================
[email protected]
www.smar.com
 
A

Armin Steinhoff

Jonas Berge wrote:
>I did not say FF has the broadest range of equipment of any bus, I
>specifically said that FF has most products for "process
>instrumentation". If you look at the list of registered products
>(http://www.fieldbus.org/ProductsAndServices/RegisteredProducts/)

I found this tiny list not very impressive :)

>I am
>sure that you will not find a similar selection of transmitters for
>flow, level, pressure, temperature, conductivity, pH, valve positioners
>and electrical actuators, controllers, on/off valve couplers, analyzers,
>converters and recorders etc. based on any other protocol (at least not
>purely digital).

Please, make simply a search with Google and PROFIBUS PA and you will find most of your finest names of the FF list in the search result .. and
much more.

> This is not misinformation.

IMHO ... your probably misinformed :)

>Like you said, protocols are designed for specific things. Arundhati
>asked about process control, which is what FF was designed for. For
>another task some other protocol may work better.
>
>I'm based in Singapore where many of the FF members have their regional
>head quarters. FF has also established an end-user council and a
>committee for manufacturers so the regional support structure for FF is
>pretty good.

Interesting ... what about the support for PROFIBUS PA ??

Best Regards

Armin Steinhoff
http://www.steinhoff-automation.com
 
J
The PROFIBUS site also has a page where you can get a listing of all products, using e.g. the PA protocol. After separating instruments from
services, development components, and networking accessories, I find that the range of products is not bad - but still smaller than for FOUNDATION(tm) Fieldbus.

Though several established process instrumentation companies are listed as suppliers of PROFIBUS PA, many such as: Honeywell, Yokogawa, Dresser, Flowserve, Limitorque, Rotork and Yamatake are not listed.

Jonas Berge
==================
[email protected]
www.smar.com
 
Simple - modbus

This is because it is the most widely used protocol out there. Try to find an OIT that speaks Foundation Fieldbus or even the dreaded HART. HART is by far the WORST of the bunch. Some protocols specify the physical layer, but most can be implemented on other physical layers as well.

Profibus would be a close 2nd, but is not as open, and requires fees.
 
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