Common sense

Sensors are now found in a wide range of applications, from tiny consumer gadgets to spacecraft. But the industry is still growing — and some markets are expanding fast.

Although sensors have been on the increase in industry, the home, the office and practically all types of consumer products over the past 50 years, they are showing no signs of saturating their markets. Indeed, as the technologies improve, costs fall and the need to sense and measure grows, they are finding ever-more applications.

The parameters that various types of sensors have been detecting include an alphabet of variables, such as acceleration, chemicals, electrical, flow, force, humidity, torque, vibration and vision.

Since the beginnings of ‘electrical measurement of non-electrical parameters’ in the late 1970s, the quality of a measuring system has depended mostly on the skills of the manufacturers, who combine precision mechanics with electrical signal sensors.

This is how systems such as a bourdon tube connected to a potentiometer enabled electrical measurement of the ‘nonelectrical’ pressure level.

Sensor products were structured so that all components of the measuring chain were stand-alone ‘black boxes’ connected in series.

Semiconductors have been used for sensor applications since the mid-1970s, and system integration was advancing at the same time, proving to be the domain of small firms which had previously specialised in precision mechanics.

If the optimisation of semiconductor technology was a first revolutionary step, the second was more evolutionary. It was brought about by the miniaturisation of measuring systems — enabling chemical process analysis to ‘wander’ out of the laboratory into the chemical plant, and thus become on-line-capable.

There are four main technical changes influencing developments: onboard intelligence, semiconductor developments, miniaturisation and sensor bus technologies to enable attachment to distributed networks, such as in plants or factories.

Smart sensors using microcontrollers are adding intelligence and functionality  to established sensor technologies for a simpler, more intuitive set-up. Depending on the sensor type, some or all of the four innovations are driving sensor markets into adopting the new technologies, such as smart sensor capabilities, wireless communications, microelectromechanical systems (MEMS)-based components, and plug-and-play sensors, with increased precision.

For communications applications, hard-wired network communication is likely to continue — until and unless wireless control of critical processes is permitted by health and safety legislation — to be an important factor in the industrial sensor market.

However, sensors designed for wireless data gathering and condition monitoring are beginning to come on to the industrial scene. For systems suppliers such as Invensys the current state of affairs is good news as they can sell both wired and wireless solutions to their industrial clients.

Certain relatively simple sensing devices, such as discrete output or analogue output industrial proximity/position sensors have not generally justified investment in integrated bus connectivity hardware, but this is changing as integrated circuit prices and cost per node of controllers fall. Otherwise, ‘concentrator’ blocks remain the economical alternative for networking simple sensors to buses.

Though wireless communication is available for industrial use, it hasn’t exactly ‘arrived.’ Currently, Bluetooth and ZigBee technologies are the primary contenders.

ZigBee standard is a good choice for low bandwidth, low-power applications. Bluetooth, like ZigBee, opens up the possibility of cost-effective, efficient, wireless sensors where data bandwidth and range are more important.

The potential wireless market has led to development in low-power electronics and high-density, low-cost, and safe energy storage devices, as the high power consumption of current sensor designs remains a critical impediment to long-term, cost-effective operation.

Packaging designs are also evolving to address speciality applications, environmental concerns, and to increase their operating life. Commonly-used materials, such as plastic, stainless steel, and plate metal, are expected to evolve with UV-rated plastics for outdoor use, and FDA-approved materials for use in food and beverage applications, as well as higher grade stainless steels from 304 to 316.

IEC enclosure ratings are becoming universally recognised, and new ones are being added to address the need for improved sealing characteristics.

According to Randy Ray, chief design engineer at Hyde Park Electronics LLC/Schneider Electric, a revolution in miniaturisation is underway.

‘MEMS are now widely used in pressure sensors and are likely to be applied to other industrial sensor technologies, such as ultrasonic and capacitive proximity/position, force, chemical, and inertial sensors,’ he said.

‘The maturing of MEMS fabrication and packaging technology will lead to lowcost, miniature smart sensors with additional capability — at lower costs.’

The industrial sensors market remains strong as competition and technical development push functionality higher and prices lower, so justifying their use in previously unmonitored machinery and processes.

One of the main new developments in sensor technology is the growth of optical techniques, based on analysis of a sample using refraction, diffraction or run-time measuring in the UV or IR range, visible light as well as ultrasound monitoring.

A recent survey reports that growth in demand for photoelectric and photointerrupter sensors will be the largest contributor to the overall growth in the north American proximity and photoelectric sensor market.

Venture Development Corp forecasts a compound annual   growth rate of 5.8 per cent for the two sensor types to 2007. Markets for photoelectric and photointerrupter sensors comprise 41 per cent of the $617m (£360m) market, the largest share of the overall 2004 north American proximity and photoelectric sensor market.

Typically, photoelectric sensors are deployed in materials handling, packaging equipment, and electronics/ semiconductor manufacturing equipment applications. Office automation equipment applications account for nearly half the shipments of the photointerrupter sensors.

Factors influencing this growth in demand, particularly in food and beverage, medical equipment, and office automation equipment markets, include requirements for non-contact detection, long life, high-reliability, high-precision, high-speed response, and sub-miniature design.

One indication of the importance of the sensor market and its booming business is the growth of the sector’s industrial exhibitions.

As with so many areas of industry and technology, the European trade show heartland in is Germany, where a merger between two sensor shows is set for next year.

MeasComp and Sensor+Test will unite as The Measurement Fair and be held annually at the Nuremberg exhibition centre.

‘MeasComp was the best-known platform for professional measuring technology and attracted an international response. The merger will make this the world’s biggest trade fair for industrial sensors, test and measurement, including components, technologies and services,’ said Klaus Jansen, MeasComp organiser.

Another big sensor-related show, Vision, will head to the larger site of the new Stuttgart Fair.

Michael Dams, director, central Europe, at National Instruments, said: ‘We are pleased. NI will increasingly be devoting attention not only to measuring technology, but also to the other aspects in the many phases of development. The Nuremberg venue and the themes of the fair offer excellent conditions for this.’