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6 scenarios for Sensor Technology

6 scenarios for Sensor Technology

Wash-down sensors survive extreme conditions

Mulheim an der Ruhr, Germany-As with all consumer products, the making of washing machines must be highly automated to minimize manufacturing costs. The drums for washing machines are produced on a production line where each drum passes through a number of drilling and milling operations. During this stage of machining, a large quantity of fluid is used for lubrication and cooling. Consequently, sensors required for detecting positions of the drums at the various points on line must be capable of withstanding the contaminating effects of the fluid.

For this application, one manufacturer uses wash-down inductive proximity sensors from Hans Turck GmbH & Co. AG. Oliver Marks, product manager at Turck, reports that because the company's WD Series sensors have proven themselves on a production line for machining automotive-engine cylinder heads, the sensors seemed the best solution for the wash-drum application. Designed for extreme conditions, the WD sensors are sealed in stainless steel barrels with front-caps and a special Viton seal, making them resistant to the machining fluids. During development, Turck used temperature shock tests, extended storage at high and low temperatures, and an insulation test to ensure the sensors are capable of withstanding wash-down cleaning with high-pressure water or steam jets. Mark says the sensors are also good for the foodstuffs industry, another important field of application for the WD sensors.

For more information, Tel: (800) 544-7769; Fax: (763) 553-0708; www.turck.com, or Enter 545

Pressure sensors measure engine conditions

Groby, Leicester, England-To monitor pressure in systems such as power steering, air conditioning, fuel, and brakes on their XKR supercharged test car, Jaguar uses the PMP 317 Series of pressure transducers from the British manufacturer Druck Ltd. The compact and rugged design of the silicon transducer enables it to provide accurate and reliable pressure measurements even under extreme conditions of temperature, shock, and vibration. The heart of the PMP 317 Series is a micro-machined silicon sensing element that mounts within a high-integrity pressure module made from stainless steel and Hastelloy, a nickel-based, corrosion-resistant alloy. This design provides hostile media compatibility and high overpressure ratings. The PM 317 can be powered directly from the vehicle battery, even during the cold-start cycle.

Such pressure data helps assess the performance of all the car systems, both during and after the tests. Once Jaguar is satisfied with each system, the design is approved and the pressure data is archived for future use, enabling the company to reduce development time on future models. Jaguar Instrumentation Project Engineer Chris Golds says, "The PMP 317 Series provides optimum performance in extremes of operating conditions. It is fully compatible with our data-logging system and we can confidently install it in areas which would be considered too hostile for many other pressure transducers."

For more information, Tel: (203) 746-0400; Fax: (203) 796-2494; www.druck.com, or Enter 546

Laser sensor triggers CCD camera

Dusseldorf, Germany-During the automatic assembly of spark plugs, a feeder system from Rhein-Nadel Automation of Aachen, Germany automatically delivers electrodes to the assembly machine. The electrodes must be fed in the correct orientation or otherwise ejected. This is achieved by a combination of light section sensor and a CCD camera. The image provided by the CCD camera passes to an image processing system then image processing software evaluates the variation of electrode thickness over its length to check electrode orientation prior to assembly. The light section sensor triggers the CCD camera when an electrode is in the appropriate position for an image to be recorded.

Winfried Feldmann, sales engineer with Sick AG, says "The light section sensor must be able to detect small round shapes, and must give a continuous signal for the CCD camera during the complete passage of the electrode through the monitoring window." Other system requirements were acquiring the entire 20 mm wide feed conveyor, and mounting it without obstructing the camera's field of view. "Of course," he adds, "the cost/performance ratio had to be right too."

Sick's DMH Light Section Sensor fits this category. The compact sensor produces a line of red light across a width of 25 mm using a laser beam, covering the complete width of the transport conveyor. With the press of a button, its teach-in system stores the reflected signal from a correctly orientated electrode as a reference. Moving electrodes are then detected as a variation in height, and a continuous output signal is generated over the length of the electrode. The output signal passes to the CCD camera to trigger it, enabling the image processing system to obtain a full image of the electrode to determine its orientation and alignment. The CCD system then provides a pass or eject signal to the feeder.

For more information, Tel: (800) 325-7425; Fax: (952) 941-9287; www.sickoptic.com, or Enter 547

Optical sensors ensure jam-free packaging

Tettnang, Germany-Colorful packaging can be essential for the success of the product it contains. Ravensburger AG, a well-known German games manufacturer, uses automatic packaging machines to fold cardboard boxes, cover them with printed paper foil, and place the lid on the box once it has been filled. Various types of optical sensors monitor the flow and position of the packaging materials and folded boxes. But the variation of contrast and color that is essential for marketing can pose a problem for optical sensors operating on the principle of reflected light. Those sensors that measure the intensity of light reflected from the object surface cannot be used in this application due to changing colors on the packaging.

One method of overcoming this problem is to use sensors that detect the surface by measuring the angle between the transmitted and reflected beams. This is the principle used by HD11 Series sensors from wenglor sensoric GmbH. On the Ravensburger packaging line, these sensors detect the presence and positioning of the lid before it is placed on the filled bottom part of the box. Equipped with a background suppression circuit, the sensors can detect the boxes irrespective of how much light is reflected by the various colors. The transmitter emits a beam of light 2 mm in diameter. The receiver, built into the same compact housing and separated from the transmitter by 8 mm, detects the beam. An integral potentiometer adjustment provides range variation from 40 to 120 mm, while a transistor switch in the sensor signals detection of the box to the machine controller.

For more information, Tel: (937) 324-1000; Fax: (937) 324-1560; www.wenglor.de, or Enter 548

Collimated LED gives laserlike performance

Wemmel, Belgium-Banner Engineering's L-GAGE(TM) Q50 Light-Gauging Analog Output Sensor gives laser position-sensor performance at one-third or less the cost of a laser-based sensor, according to Technical Marketing Manager Mike Dean. He notes the key to achieving this precision is the exacting spherical lens bonded to the LED light source, resulting in a highly collimated beam of infrared or visible light, depending on the LED used. Another lens focuses this beam into a 15-mm diameter spot for use in tight spaces or on small targets. An image of the spot on the target passes through another lens into a detector to determine target position.

The Q50's microprocessor eliminates the need for a separate controller, easing set-up time using a built-in teach mode. With a visible red LED, sensing range is 100 to 300 mm, and with an infrared emitter, range is 100 to 400 mm because of the detector's greater sensitivity at this wavelength. The user can select an output response speed of 4 or 64 msec. The sensor is designed for use in applications including dry-bulk level measurement, package filling, and loop control.

For more information, Tel: (888) 3 sensor; Fax: (763) 544-3213; www.bannerengineering.com, or Enter 549

Capacitive sensors offer fast coaxial measurement

Ortenburg, Germany-Headquartered in Brazil, Embraco is a big manufacturer of compressors for refrigeration units. To achieve best efficiency and service life, Embraco requires that the bushes fitted to the small-end piston assembly in the compressor must conform to an exacting dimensional specification. Therefore, 100% bush inspection prior to assembly becomes a worthwhile production step. The problem, however, is how to do this quickly, accurately, and efficiently.

Measured bush features include inner and outer diameters as well as coaxiality.

A DIMENSIONCONTROL measurement system from Micro-Epsilon Messtechnik makes this possible. The system rotates the bushes in a special measurement head which serves two stations. One station measures each bush; the other marks, ejects, then loads and accelerates a new one. Capacitive sensors in the capaNCDT Series 600 from Micro-Epsilon measure the bush parameters.

To determine coaxiality, inner and outer diameters at both ends of the bush must be found. Three sensors arranged in a 120 degrees star configuration at each end measure distances to the outer surface of the bush. Two sensors integrated into an arbor monitor internal diameter. These sensors mount exactly opposite a pair of outer sensors, enabling the internal diameter to be determined from the outer diameter and wall thickness. The inner sensors are ground with a round face for a snug fit in the bush, but this modification produces non-linearities in the measurement that are taken into account in the system software. During the measurement, the bush is rotated through one revolution in an air bearing which has almost no play and is not subject to wear.

Assessing performance, Achim Sonntag, Micro-Epsilon's systems development manager says, "A measurement accuracy of two micrometers and a cycle time of four seconds means precision is maintained with high production efficiency." He adds that benefits to the customer are significant, because the fully automatic facility replaces a time-consuming random sample inspection using a coordinate measurement system.

For more information, Tel: (919) 787-9707; Fax: (919) 787-9706; www.microepsilon.com, or Enter 550

Color sensor checks sugar quality

Bevtft, Denmark-Until recently, the measurement of sugar color-an important quality criterion-involved taking samples and then conducting photometric measurements in a laboratory.

To provide a continuous measurement, British Sugar installed ColourQ 2100 color measurement systems from Neltec Denmark A/S. The ColourQ 2100 comprises a transmitter that flashes light onto the moist crystalline sugar transported by conveyor, and a receiver that accepts light reflected from it. The transmitter flashes eighteen times every second; the receiver averages the reflected pulses over one second to allow for variations such as sugar level on the conveyor belt. The conveyor, transmitter, and receiver are completely enclosed and conditions inside are harsh. The air is hot and close to 100% relative humidity. Moist sugar crystals are present in the air and are deposited on any unprotected surface. Consequently, internal heaters in the transmitter and receiver prevent condensation forming on the optical surfaces.

The refinery produces different sugar products and the ColourQ measurement is used in deciding to which silo the products are routed. Geoff Parkin, British Sugar's scientific operations manager, reports, "Laboratory measurements used to take from 15 to 20 minutes and one measurement per hour was a realistic rate. This limited our process control. With the Neltec system we now have a continuous measurement enabling us to more easily optimize centrifuge performance."

For more information, Tel: +45 7451 4590; Fax: +45 7451 4641; www.neltec.dk, or Enter 551

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