TechArchive

Original article date: May 1998

No-one wants to be caught with out-of-date technology that has to be replaced at great expense. One such example is fieldbus systems which like many emerging technologies are approaching a crossroads where a shake-up is likely to reduce the number of competing operating standards.

Caught in a dilemma few businesses are prepared to take the plunge and earmark substantial benefit. This is despite the proven benefits of fieldbus technology which allows any number of pieces of production equipment to communicate with a central PLC using digital and analogue signals. On the other hand fieldbus systems produce substantial savings in installation costs.

While fieldbus manufacturers manoeuvre for position shrewd users are hedging their bets and taking steps to ensure that their products can operate whatever fieldbus protocol is installed. This is the approach which Applied Weighing has taken with its load cells and electronic weighing systems. We believe that many companies have delayed going down the fieldbus route because they are unsure that their products can operate whatever fieldbus protocol will prevail in the long term.

Applied Weighing manufactures a range of durable weighing systems that handle loads from 20kg to over 60 tonnes for a variety of industries. The company’s load cell amplifiers and load controllers can be used with any fieldbus technology. Amplifiers can be fitted with additional circuitry and different modules attached to load cells to suit the fieldbus protocol in operation.

A drawback of current fieldbus systems is that communication channels used by the modules attached to individual pieces of equipment do not always operate as efficiently as they could. Often there is spare signal capacity which is costly to run. They frequently require different isolated power supplies for digital or analogue signals.

On the plus side the benefits include lower installation costs and improved cost/performance ratios in applications linked to a fieldbus. By using digital rather than traditional analogue signals fieldbus systems can transmit data more quickly and cost-effectively. A fieldbus can connect to a wide range of devices in a manufacturing or production process such as motors switches controllers transducers and sensors. Once fitted with a special communications module each piece of equipment in the fieldbus can gather and transmit key operating information to a PLC or a central control unit. This smart device on the equipment can even detect malfunctions if they occur.

The core of the fieldbus system is a single fibre optic or high speed data cable. Instead of running separate cabling to each piece of equipment there is has one link which can be added to easily when a new plant is introduced. It also means that if equipment goes down the cabling does not have to be pulled up to uncover and resolve the faulty wiring.

As fieldbus systems become more user-friendly more companies are likely to take the plunge and reap the benefits. In the meantime it seems likely that for many the key concern will be whether or not their manufacturing equipment stands up to the compatibility test.

• John Treacy
• Applied Weighing
• 0118 946 1900

May 1998