Pneumatic And Hydraulic Equipment Page 297

POSITION FEEDBACK CYLINDER ADVANTAGES Highly accurate: infinite resolution, linearity of 1 percent of full stroke, 0.001" repeatability Less than 0.75" longer than conventional magnetic piston cylinders Reduces weight and size Repairable Internally-lubricated seals Standard wipers and piston bearing strips for long cylinder life Optional bumpers Choice of standard 6" lead wire or 3-pin connector Electronic controllers available for dual set point and scalable analog output applications Rear head cap can be rotated for optimal positioning of lead or connector Ideal for applications where magnetic position sensing is impractical, where variations in cylinder speed or stroke are needed, or where an operation requires constant monitoring of cylinder position. How it Works The Bimba Position Feedback Cylinder contains a Linear Resistive Transducer (LRT) or potentiometer mounted in the cylinder rear head. The LRT probe, which has a resistive element on one side and a collector strip on the other, is inside the cylinder rod. A wiper assembly is installed in the piston. As the piston moves, an electrical circuit is created between the resistive element and collector strip. The resulting voltage is directed externally via wiring. The output voltage is proportional to the wiper position on the resistive element, which allows the cylinder position to be determined. For example, in a 12-inch stroke cylinder, the output voltage would be 0 VDC when fully retracted and 10 VDC when fully extended. Voltage readings of 2.5 and 5.833 VDC would indicate cylinder extensions of 3 inches and 7 inches. The accuracy of an LRT is determined by three factors: resolution, linearity and repeatability. Resolution refers to the smallest change that can be detected on the LRT. The Bimba LRT has infinite resolution, and can be divided into as many parts as the electronics allow. For example, with a 12-bit, 4096-part controller, the stroke could be divided into 4096 parts. When 10 VDC are placed on a 10" cylinder, the smallest detectable increment would be 10 VDC 4096 = 2.4 millivolts or 0.0024". Resolution is stroke sensitive, i.e., the longer the stroke, the less resolution. Linearity refers to the maximum deviation of the output voltage to a straight line. The Bimba LRT's linearity is 1 percent of stroke. Repeatability is the ability of the LRT to provide the same output voltage relative to a unique cylinder position each time the cylinder is cycled. Repeatability of the Bimba Position Feedback Cylinder is 0.001". Hard chrome-plated carbon steel piston rod with blackened threads and wrench flats Sintered bronze rod bushing Internally lubricated piston seal and rod wiper 304 stainless steel cylinder body Anodized aluminum alloy end caps Standard 6" lead or optional 3-pin connector B I M B A Bimba JHF Catalog [ Volume 7 ] (314) 427-0600 800-444-0522 (FAX) 314-427-3502 www. j hf.com 297 Prices Subject to Change Without Notice John Henry Foster pneumatic and hydraulic equipment

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