SENSOR+TEST began its three-day conference and exhibition program in Nuremburg on May 30 with 550 exhibitors and nearly 10,000 expected attendees. New this year was the addition of MeasComp, a previously independent trade show dedicated to measurement applications in the automobile industry.
If there’s one thing that seems to be a common denominator of show attendees, it’s the automobile industry. Domestic German car production exceeds 5 million units annually so there is a rich variety of engineers from auto manufacturing companies, OEM machine builders, and auto parts manufacturers who are interested in the latest sensors for their products. Combine this with those who test everything in the industry, from the machines that make the cars, the cars themselves, and all the parts that go into the finished product and you have most of the audience at SENSOR+TEST. An interesting hall to be in was the “Action Area” where shiny Audi A6s equipped with the latest test gear demonstrated various applications such as collision detection.
There were other areas of interest, for those not directly involved with automobiles. Some of the most unusual examples were one company that was showing a mini-encoder system sampling toothed wheels at up to 70,000 rpm (Lenord+Bauer, Oberhausen, Germany); another company with laser interferometers (Sios, Ilmenau, Germany) measuring distances up to two meters with a resolution of less than one nanometer, used for calibrating of measuring and tooling machines; all-weather radar sensors with ranges up to 20 meters, used for collision detection (Micas, Oelsnitz, Germany); thermal cameras for the glass and steel industries that measure temperatures to 3,000 deg C (Keller HCW, Ibbenbüren, Germany); a Swiss manufacturer (IST, Wattwil, Switz.) with “the smallest humidity sensor in the world,” in SMD technology, while a Bavarian company (Ahlborn, Holzkirchen, Germany) was showing, in effect, the entire weather chart: air temperature, humidity, barometric pressure, wind speed, as well as precipitation amount, duration, and intensity in a single output signal.
‘Seeing’ with your ears
The world’s oldest sensor — the microphone — is finding a surprising new application in mechanical engineering. Highly refined, miniaturized versions are today providing new ‘vision’ into machine and automotive processes that ordinary heat, position, and vision sensors can’t provide. It all began when engineers at Berlin-based research and development institution GFaI (Gesellschaft zur Förderung angewandter Informatik; www.acoustic-camera.com) asked the question, What would the world around us look like if we could see it through an acoustic camera?
By clever arrangement, they have constructed arrays of 32 to 72 microphones and placed them in front of a sound-making devices they want to investigate, which could be something as small as an automobile engine or as large as a chemical plant.
Joachim Feierabend from GFaI brought a sewing machine to the show to demonstrate how the system works. Centered on the microphone array is a web cam pointed in the same direction, so a video image can be recorded at the same time, and the sound ‘image’ superimposed on top of it. The results remind you of thermographic images from infrared cameras, except now the red and orange highlight areas of intense noise while the green and blue colors show lower activity. What’s especially striking: recording videos of the subject, and to watch how the sound changes over time: a perfect way of capturing an intermittent fault that snapshots won’t always show.
The array of microphones works because the sensors are spaced at intervals and pointed in slightly different directions, so sound sources are pinpointed by triangulation. Feierabend showed another interesting arrangement of the microphones: a spherical array for work inside cars. Coupled with 3D CAD images of the interior, the acoustic camera can literally “look around” and “see” where the rattles car coming from.
Finding faults in tires
Tire makers are today, understandably, more apprehensive about manufacturing faults that may lead to failure on the road. Fortunately, a relatively new application of high speed laser sensors can help them with the task of finding small irregularities in the side wall surface that may indicate potential problems. Johann Salzberger of Micro-Epsilon (www.micro-epsilon.com) was demonstrating how his company’s new scanCONTROL 2800 laser profile sensor searches for bumps on tires and can find irregularities as small as a few tens of microns.
The sensor makes use of the triangulation principle for two-dimensional acquisition of profiles. The line optical system projects a visible red laser line onto the surface of the tire and the back scattered light from the laser line is registered in a CMOS array by the optical system. With the known distance information the controller computes the position along the laser line from the camera image; as the tire rotates under the laser, the measurement becomes three dimensional.
The key to making this technology work for the tire industry is to speed it up, says Salzberger, because manufacturers don’t want to spend more time than they have to in inspection. The specially developed CMOS array supports the illumination of the next image while the current image is being read out. And instead of a “rolling shutter” as is used on conventional scanners the scanCONTROL uses an electronic shutter which eliminates distortion and helps achieve short throughput times. Finally, the controller’s FireWire interface enables high bandwidth output and allows the control of multiple systems from a single PC.
A look on the surface
We’ve all heard the adage that you can’t tell a book from its cover, and most of us continue to believe it, but the spectroscopy innovators at inno-spec GmbH (www.inno-spec.de) think there’s a lot you can tell by just looking a the surface of things, and encourage us to have a second look. With some of their high-tech spectroscopy equipment, that is.
Oliver Grass was at SENSORS+TEST to show is company’s equipment can characterize an object by simply shining a light on its surface and taking a look at the reflected absorption spectrum. Unlike machine vision, the spectral imaging makes color, chemical, and geometrical characteristics digitally identifiable and therefore classifiable. Organic and mineral substances, which otherwise might require laboratory analysis, are especially easy to identify in this way.
Mr. Grass explains his company’s major contribution to work in this area has been the invention of a multichannel fiberoptic sensor head which combines more than 100 measuring channels and makes very fast material characterization possible. A typical application might be sorting recycles wastes (in the future Germany will distinguish between different types of plastics to be recycled) which requires a fast response.
Mr. Grass also thinks his system will have application for non-homogenous substances, such as meat and food products, but this will require more sensors looking at the same object, since an average reading over a number of spots must be obtained. The multichannel sensors and cables make this practical, as he demonstrated with an apple.