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Sensors networks and measurement device networks.

Sensors buses

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  Automation > Resources > Techniques > Networks > Instruments networks  

  Control buses for motion and robotics

Hart modem technology basics  


DIN-MessBus, GPIB (IEEE 488), HART protocol, HART modem, LXI modem, M-BUS (Meter bus), Profibus-PA.

Process Networks Dedicated To Measurement Devices

Instrumentation networks are specialized industrial communication networks allowing automation devices to exchange data with instruments, devices and other systems dedicated to the measurement and to analogical commands.

They can be measures transmitters, commands transmitters, or software applications used to adjust, to calibrate and to diagnose the instruments.

All of these measurement networks are used to communicate with process sensors and actuators transducers.

Generally, their main purposes are current data sending and receiving, other purposes are setting the configuration, adjusting and calibrating the instruments and their interfaces.

Another important usage is the exchange of data for sensors and actuators maintenance and control.

DIN-MESSBUS - The Measurement Bus

DIN-MeßBus features, Technical resources.

Low Cost Network Interface For Measuring And Testing

DIN-MESSBUS is a full duplex low cost network using a master-slave architecture which has been expressively designed for industrial measurement communication usages.

"DIN-MEßBUS" is also named "MEASUREMENT BUS" (which is the English translation from the German language indeed).

One of its particularities is that once the polling has started, a slave node can be disconnected and connected, an eventual interrupted data transfer will restart and continue without any data lose.

Its main characteristics are its simplicity, its robustness, its free topology, and the simplicity of its medium based on the so popular RS 485 standard.

Its message structure allow to transmit measurement values, configuration and diagnostic data.

Due to its flexibility and to its simplicity, "Din Messbus" is also used to carry quality data (for quality management), to process control and manufacturing control.

DIN-MEßBUS Features And Technology

DIN-MEßBUS Technical Papers And Resources  


GPIB (General Purpose Interface Bus), HP-IB and IEEE488

Technology overview, Programming tutorial, Fundamental knowledge.

A Standard Instrumentation Network For General Usages

The "IEEE-488" bus was developed to communicate with smart instruments (that is programmable), and to provide a standardized interface to exchange data between devices from different manufacturers.

The Hewlett-Packard company initiated the development of this versatile interface, and called it "HP-IB" (Hewlett Packard Instrumentation Bus).

Since "HPIB" became very popular, the "IEEE 488" commission renamed it "GPIB" (General Purpose Instrumentation Bus).

The "IEEE 488" medium is a 24 twisted pairs (parallel cabling), 8 pairs of them are used by the data lines to transmit the data and the command messages (for a data length of 7 or 8 bits), 5 cables are used for the bus management, and 3 cables are used for handshaking.

Later, the "IEEE 488" has evolved leading the "IEEE 488.2" version, with the integration of the SCPI interface (Standard Commands for Programmable Instruments interface), in order to avoid devices manufacturer extensions, and to provide a quite universal "GPIB" programming interface.

Introduction To The GPIB Bus Technology  

This well written and well illustrated page resumes all you need to quickly know about the HPIB bus : its history, its relevancy, its communication model, how it works, its commands, how the data are transmitted, plus the addressing, the message structures, the state model, the connector and a lot of things more.

GPIB Programming Tutorial  

This paper introduces to the GPIB bus and presents the communication principles (commands, queries, data and events), the programming rules, the instrument status, the trigger mechanism, the error codes and more. - Author : Free University Amsterdam (

GPIB Basic Knowledge  

This tutorial presents the "IEEE 488" system, particularly the role of its different lines and the SCPI model included in the IEEE 488.2 standard. - Author : National Instruments

HART - Highway Addressable Remote Transducer Protocol

What is Hart ?, Hart modem, Hart technology, Electronic interface, Educational papers, Quick introduction.

HART As A Communication Protocol For Industrial Instrumentation

HART ("Highway Addressable Remote Transducer") is a popular digital communication protocol designed for industrial process measurement applications, based on the 4-20 mA current loop standard.

The HART protocol has been especially designed to exchange configuration data, calibration data, adjustment data and diagnostic data. It is useful for installation and maintenance jobs.

HART consists in both a hardware protocol and a software protocol.

The HART technology benefits of the low noise characteristics of the 4-20 mA current loop, and do not need any other medium than the measurement transmission line, that leads in a cheap communication system.

Since HART uses rather low frequencies to modulate the signal, the transmission rate is quite low too, but it is not important because the purpose of HART is to exchange non time critical data.

The HART technology has evolved and is now available supporting wireless medium ("Wireless HART") and Ethernet medium ("HART-IP") too.

HART Modem  

A HART modem is used as an interface to enable the exchange of data between a terminal (computer, mobile terminal, programmable logic controller) and instrumentation devices such as a measurement sensors over a 4-20 mA current loop in compliance with the HART protocol.

The "HART modem" modulates and demodulates the signal in order to read and to write the data (which is the definition of a modem, indeed).

Terminal side, the data are carried over a serial communication port (RS232, USB, Bluetooth) which can be either a real port or a virtual serial port.

A HART modem allows an automation engineer to talk with a local sensor or to communicate with a remote sensor over ethernet.

Practically, the basic connection of a HART modem consists simply to insert a load resistor serially with the sensor into the current loop, after what it is enough to connect the modem in parallel of this resistor.

HART Communication Technologies  

Consultant in industrial control and communication, Romilly BOWDEN provides a whole of informations in relation with the HART technology.

You will learn what is HART in a short introduction, the revision history of the protocol, what were the main changes and a lot of other technical informations.

More, the author delivers H-SIM, a useful utility software which help you by computing the available cable length according to the desired strength of the signal you need for a specific installation of a HART network.

Romilly BOWDEN -

The Electronic Components Related To The HART Protocol  

This huge folder presents the available techniques in use to implement HART communications into hardware, and concentrates on the electric and electronic point of view.

In addition, the HART data exchanges process is explained clearly in a very detailed manner.


HART Technical Papers  
HART Technology Overview  

The "HART Communication Foundation" provides short overviews about HART communication protocol, including HART over 4-20 mA curernt loop, Wireless HART communication protocol, HART-IP Ethernet protocol, and presents the history of the protocols, what they are, and how they work.

In the technical articles section, you can download the "application guide", a 194 pages document quite well illustrated which presents quickly all the concepts in use and some industrial applications.

LXI - Network-based Extensions For Instrumentation

What is LXI ?, LXI basics, specifications and resources.

A Fast And Open Network For Instrumentation And Tests

LXI (Lan eXtension for Instruments) is an instrumentation network standard system particularly used for test instrumentation in research and development departments.

LXI is an evolution of the VXI / PXI systems which is based on the Ethernet standards, and which integrates the GPIB measurement capabilities.

LXI is GPIB compliant by networking through a dedicated gateway. In many ways, LXI is the successor of the GPIB bus.

Since it uses Ethernet, LXI benefits of the internet capabilities too, by embedding a web server into the instruments, interfacing and controlling them with a web application running on a cheap personal computer for instance.

Consequently, the devices do not need any front command panel any more, and the usage of popular and widespread technologies contribute to minimize the costs.

In order to provide an efficient synchronisation process, LXI uses the IEEE 1588 standard.

The inheritance of the VXI / PXI capabilities, of the Ethernet and internet features, of the GPIB measurement performances and of the IEEE 1588 services leads LXI to be a very powerful, fast, flexible, reliable and compact test equipment network system.

(*)  VXI (VME eXtension for Instrumentation) is a compact instrumentation network system which integrates the best features of both VME (Versa Module Eurocard) and GPIB buses.

(**) PXI (PCI eXtension for Instrumentation) is a more recent instrumentation bus system, which incorporates the leading characteristics of the PCI (Peripheral Component Interface) and of the GPIB buses altogether.

LXI Specifications And Technical Resources  

The LXI consortium promotes the LXI technology and is only too happy to offer many informations.

The "About LXI" section introduces to the technology (what is LXI ?, what are its benefits, what are its main features).

The "resources" section provides good introductions to LXI standard and some other guides. You can also download there some LXI technical papers and watch some videos. A few tools are available too.

Last but not least, you can download all the specifications freely, including the current version and older versions.

M-BUS / EN 13757 - The Meter Bus For Power Distribution

What is M-Bus ? , Meter-bus overview, Meter Bus technical documentation.

A Standard Network Interface For The Industry Of The Energy

"M-BUS" ("Meter Bus") is a specialized network dedicated to quite smart measurement devices, especially whose operating in the industry of energy and in the power distribution areas.

METER-BUS is particularly used to read consumption measurements at low cost.

There are several current available implementations, the last one supports wireless communications.

"M-bus" is a rather versatile network since it uses linear topology, star topology, tree topology or wireless network architecture, using a single master / slave structure and a client / server communication process.

One of its specificity is (or was) that the data telegram are not specified, letting the manufacturers free to define and to specify it.

In its wired versions, another "meter bus" specificity is that the master and the slaves modulate the signals over the power line in order to communicate.

METER-BUS Technical Overview  

This good overview about the wired system presents the "meter bus" data transmission system, the topologies, the "Meter-bus" trunk, applications and some related software.

Initial M-BUS Technical Documentation  

The "M-Bus" organization provides the complete M-bus V 4.8 technical documentation ( ), an old version in which you can learn the fundamental principles of the meter bus system.

PROFIBUS-PA - Profibus For Process Automation

Profibus Alliance, Miscellaneous.

The Siemens Network For Automated Process

Profibus-PA Technical Description  

This tutorial introduces the fundamental knowledge about Profibus in general, and the basic technology of "Profibus-PA".

It explains the physical layer, the data addressing, the safety layer, the topologies, the connections, the user interface and the device description interface (GSD files and EDD files).

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