I am Juan Carlos, I am from Peru. Actually I am working in a company specialized about industrial networking.

I am a Sales Engineer, and I am learning about Fieldbus. One customer asked me information about Fieldbus and Modbus, so I want to know if Fieldbus technology uses Modbus protocol.

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
Web: www.techvalue.com.pe

 

There are many "buses", i.e. multi-node networks for IO and other communication chores. Some are just an IO bus.

Modbus was developed many years ago for what was then Modicon PLCs to communicate with one another. It is a master-slave network that runs in the 1000's baud range. Over the years it has become a de facto standard. 9600 and 19200 are very common in the applications I use. There are new clever ways like Modbus over IP that achieves higher data throughput. It is typically not used for control; but often for passing large amounts of data between dissimilar hosts.

One of the fieldbuses is Foundation fieldbus; you can learn about it in a lot of places, http://fieldbus.org , search for Plantweb university at http://www.emersonprocess.com , http://www.relcominc.com has some excellent references.

Profibus is another one, has some manifestations that remind me of Modbus and some have similarities to Foundation fieldbus. Try http://profibus.org for info.

 

Hello, I am learning about buses.

Modbus is a protocol.
Basically Modbus ASCII and Modbus RTU.
Connection is through RS 232 or TCP/IP.

How are the Smart Temperature transmitters and Pressure Transmitters connected with DCS?
They can be connected to a field bus network.

Normally the transmitters have 4-20 MA, Modbus, Fieldbus connectivity.

Regds

 

Smart Temperature transmitters and Pressure Transmitters connected with DCS
using HART (over 4-20 mA) or Foundation fieldbus (FF). HART and FF provide
power over the bus (two-wire system) and can be intrinsically safe. HART and
FF also support EDDL (http://www.eddl.org) for integrating the device information
into the DCS and device management software (part of asset management suite)
enabling devices to be setup, monitored, diagnosed, etc.

Modbus is not used in field instruments such as transmitters. Modbus
provides no power and is not intrinsically safe. Modbus does not support
EDDL. Modbus is instead used for remote I/O and PLC, etc.

FF has a number of other advantages making it the leading protocol for
digital closed loop control. For example, separation between real-time and
non-real-time communication so that device management tasks do not interfere
with closed loop control. This makes FF the best choice for any PID loop or
measurement where the value is totalized/integrated. Moreover, measurement
sampling is synchronized with control and actuation ensuring a precisely
periodic 'dt' as required for good PID control. Rigorous interoperability
testing. Automatic addressing. Online firmware upgrade. Etc.

Cheers,
Jonas