Plant Services - December 2007 - (Page 17)

TECHNOLOGY TOOLBOX Know your position Encoders can handle the environment, the application and size limitations tive analog optical encoder offers precise, real-time positionncoders are being engineered to meet increasingly ing and directional sensing. It uses a reflective code wheel or specific needs. Space considerations, environmental linear code strip to sense position and velocity. Two-channel factors and applications come into play when deteranalog signal output offers 180 lines per inch resolution that mining which encoder is best suited for a given job. When can be increased through interpolation. The lead-free packproperly matched, plants can achieve their operational obage is compliant with the European Union’s Restriction of jectives while avoiding unnecessary and costly downtime. Hazardous Substances (RoHS) directive. Physical environment: Encoders can withstand dust, Targeted applications: Dynapar’s Hengstler Acuro AX71 dirt and explosion hazards. For instance, magnetic encodabsolute encoder was designed with the help of a drilling ers and digital tachometers by Dynapar are more rugged services firm to withstand downhole conditions. Its stainthan optical rotary encoders and resistant to dust, moisture, less steel construction, IP67 sealing and bearings withstand shock and vibration. They use magneto-resistive (MR) techshock loads to 100 g. An ATEX-certified nology to track machine speed and provide housing allows it to be used in explosive endigital shaft velocity feedback. A magnetic For spacevironments without electrical barriers. The pulse wheel, imprinted with small magnetic unit’s electronics use heat-stable substrates poles and an integrated MR sensor produce constrained and diodes that ensure reliable operation magnetic fields that penetrate dust, dirt, oil applications, an to 140°F. In addition, the encoder is selfand contaminants. The wheel rotates with array of small grounding to prevent shorting. the shaft, and the sensor’s resistors change encoders is Heidenhain’s LS 688C linear encoder is value with the magnetic field. for manually operated machine tools with In harsh areas, where caustic chemicals available. digital readout. It’s scanning carriage rides and corrosive agents threaten equipment reon ball bearings, providing rigidity and liability, stainless steel encoders offer a rugtight backlash and mounting tolerances. By comparison, in ged alternative to aluminum or plastic. Encoder Products’ machine tools without linear encoders rely on the pitch of Model 865T, designed to mount on NEMA C-face motors, the ball screw, which is subject to thermal expansion, rehas a housing milled from solid piece of 316 stainless steel. sulting in inaccurate output. Linear encoders compensate An optional stainless steel cover protects internal bearings for thermal expansion, thereby keeping machine tools therand electronics from dust and machine wash-downs. mally stable and producing tight manufacturing tolerances. Another example is BEI’s H25 and H20 incremental roBuilt-in encoders are available for applications such as tary encoders, available with optional stainless steel housconveyor belts and door openers that require low-resoluing, encoder body and bearing housing. Applications are tion speed and position feedback. Bodine’s custom-made chemical or petrochemical, food packaging, medical and Incodermotors with built-in magnetic encoders are availsimilarly harsh industrial environments. able as permanent magnet DC, brushless DC or gearSpace constraints: Industrial machinery and equipment motors. The encoder is pre-wired and dropped into the is getting smaller, and so are the electronic components. For OEM’s design, reducing assembly time and protecting it space-constrained applications, an array of small encoders is from the environment. available. An example is the surface-mounted encoder series by Avago Technologies. Measuring 6.5 mm by 4.2 mm by 1.69 mm, the AEDR-8320 is useful in robotic equipment, E-mail Contributing Editor Sheila Kennedy, managing director of pick-and-place machines and other applications. The reflecAdditive Communications, at Sheila@addcomm.com. For more information, see: www.dynapar.com www.encoder.com December 2007 E www.beiied.com www.avagotech.com www.PLANTSERVICES.com www.heidenhain.com www.bodine-electric.com 17 http://www.dynapar.com http://www.beiied.com http://www.heidenhain.com http://www.encoder.com http://www.avagotech.com http://www.bodine-electric.com http://www.PLANTSERVICES.com

Table of Contents Feed for the Digital Edition of Plant Services - December 2007

Plant Services - December 2007 Contents From the Editor: Orange Alert The PS Files: Pressed into Innovation Up and Running What Works: Samuel Adams Facility Refreshed in Cincinnati Energy Expert: Energy's "Perfect Storm" Technology Toolbox: Know Your Position Cover Story: Get a Grip on the Steamer Piping: Outside Looking In Web Hunter: Potpourri X In the Trenches: Making a Big Stink Boiler Room: Getting Educated

Plant Services - December 2007

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