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Two Pulse Per Revolution Digital Tachometer

IP.com Disclosure Number: IPCOM000083128D
Original Publication Date: 1975-Apr-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Holdaway, DO: AUTHOR [+2]

Abstract

Described is a device which is capable of measuring the velocity of a rotating shaft.

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Two Pulse Per Revolution Digital Tachometer

Described is a device which is capable of measuring the velocity of a rotating shaft.

A hole 10 is bored in rotatable shaft 12. light-emitting diode (LED) 14 is mounted on one side of hole 10, as shown in Fig. 1.

Phototransistor 16 is mounted on the opposite side of hole 10. As shaft 12 rotates, light is transmitted through the shaft hole 10 twice per revolution which results in two output pulses from phototransistor 16. The output pulses are fed to a squaring circuit, not shown, and the output of the squaring circuit is fed to detecting circuitry, which determines the elapsed time between the two pulses and outputs a signal indicative of the shaft rotational velocity.

The principal advantage of this device is that LED 14 and phototransistor 16 is directly mounted to the circuit board. Also the LED and the phototransistor is completely removable and field replaceable, without alignment or adjustment requirements.

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