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Article: Improved tachometer eliminates backlash. (design ideas: volume 2, number 15A)
- Article from:
- EDN
- Article date:
- July 21, 1988
- Author:
CopyrightCOPYRIGHT 1988 Reed Business Information, Inc. (US). This material is published under license from the publisher through the Gale Group, Farmington Hills, Michigan. All inquiries regarding rights should be directed to the Gale Group. (Hide copyright information)
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Improved tachometer eliminates backlash The tachometer circuit of Fig 1 interprets the quadrature square-wave signals from an optical encoder. This circuit performs the same function as that of an earlier Design Idea ("Bidirectional tachometer offers low error," EDN, October 30, 1986, pg 204), but it reduces the IC count from 11 to 3 and produces twice as many pulses per encoder revolution. It also eliminates backlash: The FWD and REV outputs indicate the direction of encoder rotation at every transition of the tachometer signals A or B, regardless of how little the encoder rotates before changing direction.
The encoder shown is a Hewlett-Packard HEDS-7500; HP ...