Browse Prior Art Database

Digital Tachometer Improvement

IP.com Disclosure Number: IPCOM000076831D
Original Publication Date: 1972-Apr-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Coburn, RL: AUTHOR [+2]

Abstract

This is a two-phase optical tachometer whose two stationary masks 22, 23 and one movable mask 21, with energy transparent regions 25 (D) separated by opaque regions 24 (2.8D), are constructed to provide approximately a 3-to-1, dark-to-light ratio (D, 2.8D).

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Digital Tachometer Improvement

This is a two-phase optical tachometer whose two stationary masks 22, 23 and one movable mask 21, with energy transparent regions 25 (D) separated by opaque regions 24 (2.8D), are constructed to provide approximately a 3-to-1, dark-to-light ratio (D, 2.8D).

Two radiant energy sources 15, 16 are positioned on one side of disk 21, and on the other side masks 22, 23 and two associated photocells 17, 18 are oriented relative to mask 21 to provide two signals which are 90 degrees out of phase. Electrical output signal A, B of each photocell is cyclic in nature. Each cycle thereof provides an active triangular output waveform interval, corresponding to the presence of light, which is slightly larger than one-half of the total cycle time. Each of these electrical output signals is connected to the input of amplifier 26 or 27 whose sensitivity threshold is adjusted by potentiometer 28, 29 to a low value, and to a value which producers a cyclic square-wave output. Each square-wave cycle of the amplifier output is symmetrical; that is, each cycle includes an active output interval, corresponding to the presence of light, which is equal to one-half of the total cycle time.

Phase comparison network 45 compares phase relationship of the two waveforms of conductors C and E and provides an output on conductor 46, which indicates the direction of movement of disk 21. Counter 47 counts the cycles of the waveform on conductor E and provides an output...