Position Sensors

Position sensing technologies, while diverse, seem to be "well-positioned" in their application spaces—more than 95% of respondents to a recent survey indicate they'll use the same amount or more of such sensors in the coming year. Limit switches, inductive sensors and safety switches are among the most used; vision sensors are the fastest growing.

05/01/2006


Machine Control & Discrete Sensors

Diverse technologies help measure position. Of these, machine vision and magnetostrictive sensors will show the largest percentage-point growth in the coming year, survey respondents say.

Position sensing technologies, while diverse, seem to be "well-positioned" in their application spaces—more than 95% of respondents to a recent survey indicate they'll use the same amount or more of such sensors in the coming year. Limit switches, inductive sensors and safety switches are among the most used; vision sensors are the fastest growing.

In a survey of Control Engineering subscribers by Reed Corporate Research, among those specifying, recommending, and/or buying position sensors, 55% do so for in-plant requirements and 23% do so for OEM (resale) requirements and 22% do for both.

Among applications for position sensors, motion control claimed 52%; continuous product manufacturing 43%, batch manufacturing 37%, robotic equipment 29%, and tool positioning 27%. Rounding out the top 10, were packaging, material handling, discrete product manufacturing, chemical handling/process, and plastic product manufacturing and palletizing (tie).

Technology types

Eighty-six percent of respondents currently use limit switches and 81% currently use inductive sensors. Results suggest limit switches will remain the most widely used position sensor a year from now. Among position sensor technologies, machine vision showed the most anticipated growth in the coming year with a gain of 7 percentage points to 49%.

Between photoelectric and vision sensors, says John Keating, Cognex product marketing manager, is a new class of presence sensor not included in the survey. The Cognex Checker detects parts by understanding what they look like, without precise positioning. Photoelectric sensors use reflected light, which can lead to false positives. Checker can be used to detect patterns and multiple features and gives one, pass/fail result, so no PLC logic is required for an answer.

Strong survey interest in vision shows "as costs decline and vision sensors get easier to use, more people will apply them in position-sensing applications," adds Bryan Boatner, another Cognex product manager, "because of greater ability to find the part regardless of orientation, size, and changes in appearance."

Machine vision can offer more accurate positioning to reduce waste and boost productivity, suggests Robert Lee, strategic marketing manager, Omron Electronics; "Customer expectations for consistent quality are a key driver for manufacturer's efforts to make every item the best it can be."

In the survey, next largest growth after vision was in magnetostrictive sensors, 5 percentage points higher in the coming year, to 26%. Other sectors showing growth include laser sensors, ultrasonic proximity, and cable extension (reel) sensors for position sensing applications.

"With new and improved technology, the market should show a trend toward non-contact type sensors," explains L. Filipkowski, product manager, AutomationDirect. "Limit switches have always been a tried-and-true method for position sensing, but they have physical constraints that limit usefulness in certain applications. Sensors such as inductive proximity, capacitive proximity, photoelectric, and ultrasonic are being used in many new applications never thought of before.

"New technologies allow inductive proximity sensors to have longer sensing distances, smaller packages, and allow for teachable target sensing. Ultrasonic sensors are dropping dramatically in price and the styles of ultrasonic sensors are also changing," adds Filipkowski.

Among features most important to respondents when buying position sensors is ruggedness; over three-fourths of respondents rated this very important. Other features in descending order of importance are: short-circuit protection, alignment set-up aid, corrosion resistance, LED indicator for status. Rounding out the top 10 are output digital, reverse polarity protection, LED indicator for diagnostics, self-teach setup, and wash-down protection.

Majority of respondents operate position sensors closed loop (82% without operator intervention).

Standard sensors with interface modules on a device network are used by 59% of respondents; 41% use network-enabled sensors; 84% of respondents who currently use a device network apply Ethernet, and 60% currently use DeviceNet. Results suggest Ethernet will remain the most widely used device network a year from now. At present, 43% connect to Profibus; 20% to AS-i, and 20% to Interbus.

On average respondents have purchased 128 position sensors in the past 12 months. The average spending per respondent on position sensors in the past year was $29,108. Purchases of position sensors will increase by 31% of respondents in the next 12 months; 65% remain the same; just 5% predict a lower demand.

Presence sensing-related products

For more manufacturers, visit www.controleng.com/buyersguide . For system integrators www.controleng.integrators . Also visit company Websites listed.

EXCLUSIVE: Tiny magnetoinductive analog absolute linear position sensor

Machine Control & Discrete Sensors

Balluff has expanded its novel magnetoinductive BIL analog absolute linear position sensor to provide highly accurate, non-contact continuous positioning information for pneumatic grippers. Mini-proportioned and optimized to provide position control information, the versatile and innovative sensor is designed for continuous position sensing. Analog output signal allows absolute real-time sensing to detect that objects are properly secured in the gripper jaws. A tiny sensor head (for embedding in a mounting T-slot in the gripper mechanism) connects via cable to a small electronics module containing proprietary Balluff magnetoinductive technology. It senses movement of a small magnet attached to a gripper finger through the aluminum gripper fixture and is said to deliver high-resolution, analog temperature-compensated linearized stroke information up to 10 mm. Voltage and current-output versions are available. It has no moving parts (other than the magnet installed in the gripper), and sensor head and processing elements are sealed to IP65 for high resistance to shock, vibration, moisture, and common contaminants. BIL is said to be a cost-effective upgrade to conventional continuous position feedback sensing devices on virtually any short displacement motion-based system, the company says. www.balluff.com Balluff Inc.

Limit switches: small, tough

802B family of Allen-Bradley limit switches is designed to withstand today's tough industrial environments. In three rugged body styles—compact, precision, and small precision—the 802B can be mounted in areas too small for traditional NEMA-style limit switches. Each model features a die-cast housing for durability as well as industry-standard mounting dimensions and operating characteristics for optimal application flexibility. Compact style housing has a pre-wired 3-meter cable and triple-sealed construction for NEMA 6 and IP67 enclosure ratings. www.rockwellautomation.com Rockwell Automation/ Allen-Bradley

Multiple tools, 1 vision sensor

Safety

PresencePlus P4 Omni combines all P4 vision inspection and analysis tools into one compact, self-contained housing. Tools—Blob, Gray Scale, Geo, Edge, Object, and optional Bar Code Reader—make it easy to switch applications without changing sensors, the company says. Using remote Teach, the sensor can learn new inspections without connecting to a PC or shutting down the production line. P4 Omni starts at $1,995. The 1.3 megapixel model has more than 100 times the resolution of the standard Omni, providing a large field of view and performing highly detailed inspections. www.bannerengineering.com Banner Engineering

In position with 3 photoelectrics

Machine Control & Discrete Sensors

Three series of photoelectric sensors is said to offer unique capabilities often unavailable in traditional photoelectric sensor products. FARS Series is a standard 18 mm tubular diffuse sensor in a non-metal package with background suppression technology to greatly reduce false readings beyond the specified sensing distance. It has sensing distance of 30-130 mm and an adjustment potentiometer, further increasing sensor accuracy within its range. MQ Series is an ac diffuse photoelectric sensor line with unique 90imum switching frequency of 10 kHz, for high-speed counting or motion-control applications. Starting prices range from $45 to $80. www.automationdirect.com AutomationDirect

Sensor tracks, rejects parts without PLC

Safety

Checker 101E is a new model in family of sensors said to be the first and only sensors that use patterns to detect and inspect parts, providing unmatched reliability. Checker 101E offers the simplicity and power of the original Checker 101, says Cognex, and it accepts encoder signals, eliminating the need for a PLC when tracking and rejecting parts on variable-speed production lines. Shift register is automatic, enabling accurate tracking of up to 4,000 parts between the inspection and rejection points. It acquires and processes more than 500 images per second and can be used to detect and track parts or web materials for improved process control. It has step-by-step setup. www.cognex.com Cognex

Limit switches reduce cost of position indication

Machine Control & Discrete Sensors

GLL limit switch extends Honeywell's existing line of compact limit switches to meet the needs of high-volume applications. It comes in a compact and lightweight RoHS-compliant package at a price up to 40% lower than comparable products, the company says. Potential OEM applications include elevators, escalators, aerial platform lifts, packaging equipment, and industrial doors. GLL requires fewer wires to install (double insulated housing, no ground required) and offers easy access to wiring a terminal block via a convenient hinged cover, with IP65 and NEMA 13 ratings. Approvals include UL, CSA, CE, and CCC. www.honeywell.com/sensing Honeywell Sensing and Control

1st food-grade stainless steel compact photoelectric

Omron has introduced what it calls the world's first food-grade 316L stainless steel compact photoelectric sensor—E3ZM—to meet rigorous cleaning and hygiene requirements for food processing, pharmaceutical, and beverage industries, offering working life of 200 times that of conventional sensors in plastic or die-cast alloy housings. Cost savings, in maintenance labor and sensor replacement, will be significant, resulting in greater productivity and profitability, the company says. Detergent- and chemical-resistant case features minimal indents and an easy-to-clean surfaces for optimum hygiene that exceed standard quality for food processing. A hermetically sealed housing resists high-pressure water exposure that meets tough IP69K industrial rating. It is available in a variety of sensing modes: through-beam, retro-reflective, diffuse, and background suppression sensing. www.omronelectronics.com Omron Electronics

Laser-like performance, no safety concerns

Safety

Series 28 photoelectric sensors in dc and ac/dc versions feature a rugged IP67-rated housing. They bridge the gap between laser precision and visible red safety sensors—perfect for fine positioning applications. They feature a small, visible red light spot size of 4 x 4 mm at a range of 250 mm with 400 mm adjustable background suppression that enables ignoring machine surfaces and objects beyond the adjusted range. Series 28 sensors include light on/dark on selectable functionality with two PNP outputs. They offer micro M12 with a quick disconnect and front and rear status LEDs visible from any direction, up to 50 ft away. www.am.pepperl-fuchs.com Pepperl+Fuchs

Spring-loaded dc-LVDT position sensors

Machine Control & Discrete Sensors

Simplify mechanical set-up in automation applications with GHSE 750 line of 24 V spring-loaded position sensors. They offer accurate position measurement in a variety of dimensional gauging applications. Available in ranges of 0.1 to 4 in. (2.5-100 mm), the maximum linearity error is 0.25% of full-scale output. Offered in a ready-to-use package, configuration supports longer-range gauging applications. Sensors consist of a spring-loaded shaft running in a precision sleeve bearing, connected to the linear variable differential transformer (LVDT) core. With core and coil assembled into a spring-loaded assembly, mechanical setup into automated machinery is said to be simpler and more cost-effective than other sensors. Stainless-steel construction and hermetic sealing of these 19-mm dia sensors provides long service life, for applications such as electronic dial indicators, fabricated metal products gauging, materials testing apparatus, and large shaft TIR measurement. It's IP68 rated. www.macrosensors.com Macro Sensors

Non-contacting rotary sensor, no moving parts

Safety

Based on magnetic field technology, Novotechnik RFC sensors have no moving or mechanical parts to wear-out or break. A magnetic assembly fixed to the shaft is physically separated from a sensor with an embedded integrated circuit that provides analog output representing the calculated angle range, 30-360is available with two voltage output options. Applications include industrial valves, automotive suspension systems, and other usage in automotive and marine industries. www.novotechnik.com Novotechnik U.S. Inc.

Fiber-optic laser encoder, picometer resolution

Machine Control & Discrete Sensors

RLE20 fiber-optic laser encoder system provides sub-nanometer non-linearity and resolution capability of 38 picometers. It enables precision motion-system manufacturers, lab and medical instrument makers, and semiconductor equipment OEMs to meet ever-tightening requirements. Fiber-optics deliver laser light to two measurement axes from one laser source, eliminating the need for remote beam splitters, benders, and adjustable mounts. Differential measurement capability and 2 part-per-billion laser frequency stability assure highest precision control over X-Y axes. Sub-nanometer resolution capability is possible at velocities up to 1 m/s (40 in./s) and axis lengths up to 4 m (160 in.). Innovative design reduces laser alignment to a simple "bolt-down and dial-in" process. Only two components need to be aligned to form a complex axis positioning system, enabling dramatic reductions in installation time and equipment footprint. Fiber-optic cables allow remote location of the laser unit (up to 3 m) to save on workspace and keep laser heating away from a measurement axis for reduced thermal drift. The system delivers positional output signals in differential digital RS-422 and/or 1 Vpp sine/cosine formats. Digital output signals provide resolutions of up to 10 nm, while analog signals can be used in conjunction with Renishaw's RGE interpolators or a new RP120 parallel interface to provide resolutions of 0.39 nanometers and 38 picometers respectively. www.renishaw.com/encoders . Renishaw

Ultrasonic proximity, analog sensor, long range

Safety

Superprox SM906 ultrasonic proximity sensors have the shortest deadband, longest range, and smallest package on the market, the company says. Ideal for long-distance sensing, this analog sensor has a range of 8 in. (203 mm) to 26 ft (8 m). With an 8 in. deadband, it can be mounted closer to the object than most long-distance sensors. Its length of only 4.65 in. (118 mm) makes the 30-mm dia sensor ideal for mounting in tight spaces. It is factory configurable or field programmable for specific analog sensing applications. Users can specify 0-10 V dc or 4-20 mA output, directly or inversely proportional, and an output state for loss of echo and power up. Response times, including a standard 250 ms (150 ms minimum) are available, with functionality selections including foreground suppression, background suppression, and DeviceNet capability. Superprox SM906 has temperature compensation for 14-140 °F (-10 to 60 °C). www.sesensors.com Schneider Electric/Hyde Park Electronics





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