PACE 60-year Anniversary Series: Sensors
supported by ifm efector
Australian sensor experts and sensor manufacturing companies continue to develop unique ways to utilise technology to create innovative and competitive products and solutions.
For SICK Australia customer service and expert technical office manager, Ken Collishaw, the evolution of sensors is tied necessarily to the history and development of our process industries.
“The history of sensors in Australia is a critical part of the history of manufacturing in Australia. Without sensors there could be no automation, and without automation Australian manufacturers could not be competitive,” Collishaw told PACE.
Collishaw has worked in Australia’s manufacturing and process industries for 31 years, and for thirty of these years he has specialised in sensors. Launching his career with NHP in 1982, Collishaw went on to manage the company’s Schmersal, Datalogic and TER ranges of sensors up until 1987, when he moved to SICK.
“A clear memory I have from 1983 was climbing a 3-metre ladder to reach a hopper full of polystyrene beads and changing the existing and unreliable capacitive sensor for an optical device,” he said.
“Back then, it was quite common for the incorrect unit to be utilised for a job – such as the capacitive device in that case – because we really had very few specialists in the sensor field, and pretty much no training.”
For Collishaw, the major developments in sensor technology during his time in the industry include: adjustable background suppression sensors; analogue output devices – particularly distance measurement; vision systems; safety area scanners; programmable rotary encoders; and the wide-spread implementations of programmable logic controllers (PLC) and bus control systems.
“Regulatory changes have had a major effect too, particularly those pertaining to industrial safety and emissions. They have introduced markets for sensors that go beyond the traditional cost savings motivation,” he said.
Inductive proximity sensor for 2-wire alternating voltage (circa 1970s). (Image courtesy of ifm efector.)
According to Collishaw, the sensors we see out on the field today are not only physically different from the units used in the 1980s, but they also incorporate a slew of new technology and capabilities.
“Ten years ago we did not have the specialist products that exist today, such as the sophisticated barcode reading gates now commonly used in airports, and sensors suitable for use in areas where there is very harsh washdown,” Collishaw said.
“Twenty years ago we did not have the programmable rotary encoders; we only had one model of laser distance measurement; there were no safety scanners; and sensors were much larger as surface mount technology and miniaturisation in manufacture was not commonplace.
“Thirty years ago many of the sensors were still using incandescent light sources and it was much more common for sensors to have timing and other control functions on board as PLC technology was in its infancy. Housings were very large and were of heavy steel construction.”
Collishaw believes sensors are extremely important to the evolution of manufacturing as we know it, continually increasing the ability of manufacturers to make higher-quality products, faster.
“An example is in the manufacture of chocolate Easter eggs. I once saw a production line where Easter eggs had been cut in half and had to have candies added. This job was done by a worker who simply took a scoop of candies from a box and dropped them in.
"This worker did this all day. While we were installing and testing a sensor on a nearby machine I watched the worker use their free hand to slowly sort out candies into colours of football teams on the edge of the conveyor. When there was enough of a particular combination for a scoop they went into the next egg,” Collishaw recalls.
“Now, that same job is done by a simple batching machine. A sensor detects the open Easter egg is present, and the batching machine, which utilises many sensors itself, drops the candies in.
"There is less wastage, high product quality and consistency and you are far less likely to have to look at the colours of the team that beat yours on the weekend next Easter Sunday.”
Transistors and microprocessors
ifm efector managing director, David Delany, began his career in the mid-1980s as an electrical apprentice with a company that manufactured components for ships and pumps.
“My first experience working with sensors was replacing mechanical limit switches with proximity switches in a foundry in 1986. This environment was very hard: it was extremely hot and dirty and the atmosphere caused a lot of machine down-time as the mechanical limit switches would foul-up with dirt, contacts would stick and mechanical arms would bend or move out of alignment,” Delany told PACE.
“Replacing these with the new proximity switches removed all these causes of down-time; I remember the older tradesmen being sceptical of the new technology, as you could not see if the units where working – at that stage there were no LEDs to indicate status and, being solid state, you could not hear a clicking of contacts being made when operated.”
A very common visible sensor application. The sensors are detecting over-height trucks on roads as they approach a tunnel or bridge. This type of sensor has been doing this application since the late 1980s/early 1990s. (Image courtesy of SICK.)
For Delany, the invention of transistors and microprocessors have been two major milestones in sensor technology over the years.
“These advances meant you did not need bulky, unreliable vacuum tubes to switch electrical circuits. With transistors you could perform the same functions using less power and space. This lead to PLCs and hundreds of sensors which used mechanical methods of detection being replaced with smart, more reliable electronic sensors,” he said.
“Today’s sensors are smarter, smaller, more reliable, accurate and affordable than the sensors of the past. Also, connected via bus systems and being able to monitor or change values via the internet, was not even dreamed of about 30 to 40 years ago.”
Size and ability
For Pilz Australia managing director, Scott Moffat, the most noteworthy developments in sensor technology over the years have been the size of the components, and the way they are controlled.
Moffat, a chemical engineer by profession, has been working across the mining, chemicals, manufacturing and automation industries for over 20 years.
His first experiences with sensors and control systems were when he came out of uni, and began working for an American chemical company, predominantly in the mining and pulp and paper industries.
“When I first played around with sensors and instruments in the mining industry, they were massive. You had big sensor heads that you had to stick in place with big umbilical cables coming out, plugging in to boxes to take measurements – and you’d lug that all around the country side,” Moffat told PACE.
“For me the biggest thing is how fast they’ve adapted technology now to become quicker, smaller, faster, and more accurate. We used to work with some sensors that were painfully hard – you had to babysit them. They’d always fall over, and measurements were incorrect in some aspects.”
According to Moffat, one of the biggest turning points in the technology was the switch from MIMIC-based to PC-based control.
“Around the late 1980s and early 1990s, all the sensors and instruments were hooked up to MIMIC boards. Then pretty much over night that all moved to computer-based or PC-based control ,” he said.
“Although that didn't change the sensor per se, it certainly changed the way they were used. It meant you were able to have real-time trends, you could review historically a lot better how things operated, and go back in time. It just really increased the power of that instrumentation.”
In 1987 Pilz developed the first emergency stop safety relay, called the PNOZ, to protect man and machine.
Some of the major advancements in the technology have been data acquisition, wireless, safety-rated sensors, hazard area, self-diagnosing, self-calibrating and plug and play, Moffat says. He also notes the development of the Australian safety standard, AS4024.
“Around the year 2000, safety sensors started to gain traction; there was more onus and a lot stronger emphasis on separating safety from standard automation practices, and that came about with the advent of the AS4024 safety standard in Australia,” Moffat said.
“The next big thing from a safety engineering perspective is that we’re now seeing safety and standard automation combined in to one; we’re seeing those two come back together. You might see sensors come out in the future with both standard and safety functions in them.”