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Since the day of their introduction Instrumentation devices have always been required to evolve. One of the main reasons for this is to accommodate new, better and more complex communication protocols.

What a lot of people still do, due to ease of use and consistency is specify instruments with analogue or RS-232 serial communication. Analogue communication (4-20mA, 0-5v or 0-10v) and RS-232 which was the original way in which computers communicated was the original, mainly due to cost and available technology.

It is still a very robust and solid way to send and receive information over a small group of instruments however it does have some very practical set-backs. As a point-point communication protocol it requires a port both on the instrument and the controller, this can be very limiting in size affecting both the amount and length of cables needed.

The development of Fieldbus communications meant it became possible to have multiple (100’s) of instruments connected through only one communication port at the controller level. This means that you had a huge reduction in both the number and length of cables needed. This development allowed the complexity to increase and size decrease of instruments containing multiple sensors.

As with VHS and Betamax there will always be competing technologies and ‘bus’ development was no different. Of course everyone hopes for a single unified solution because it makes things simpler, cheaper and more efficient. However the reality is that most ‘buses’ are utilised differently in different industries.

Different industries are described as either; a ‘process fieldbus‘ used in many process automation applications (flow meters, pressure transmitters and other measurement devices) or a ‘device network’ which is a large number of discrete sensors are used, motion, position etc., the best example of this is in automotive manufacturing.

There is an IEC standard that was developed for the European Common Market and interestingly I have learnt that the common goal was not focused on commonality but more the elimination of restraint of trade between nations. This standard is IEC 61158, it is almost 4000 pages long. Issues of commonality are now left to the consortium that supports each of the standard fieldbus types.

What next is always a good question, Ethernet based communication systems are one area that has seen large development over recent years and its definitions are being added into the International standards.

In all of this, what is our involvement in Fieldbus. As you may know, we are mainly involved in Process and control industries. We support almost all of the major bus systems out in the market and also have our own in-house ‘Flow-bus’ system that can be used link multiple instruments together. You run them through a single PC running our Flow-Plot or Flow-View software.

The latest addition to the communication range is the ‘Gateway’ solution. This allows multiple or manifold instruments on a Flow-Bus network to communicate with PROFIBUB or PROFINET DP through a specific fieldbus interface. This can be a very cost effective solution as multiple PROFIBUB or PROFINET DP instrument can become very expensive, very quickly.

Bronkhorst Field-Bus Technology

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