Dismiss
InnovationQ will be updated on Sunday, Oct. 22, from 10am ET - noon. You may experience brief service interruptions during that time.
Browse Prior Art Database

Electromagnetic Tachometer

IP.com Disclosure Number: IPCOM000089890D
Original Publication Date: 1968-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Wehmer, BF: AUTHOR

Abstract

The tachometer generator has virtually no cogging-effect, i.e., flutter, a much lower magnetic radiation and its voltage output is uniform and independent of any speed variation. This simplifies the use of the waveshaped voltage output for frequency dependent feedback networks.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 83% of the total text.

Page 1 of 2

Electromagnetic Tachometer

The tachometer generator has virtually no cogging-effect, i.e., flutter, a much lower magnetic radiation and its voltage output is uniform and independent of any speed variation. This simplifies the use of the waveshaped voltage output for frequency dependent feedback networks.

At A, motor 1 drives tachometer elements included in housing 2. The tachometer includes a Hall element 3 positioned for reaction to cogged wheel 4 rotated by motor 1. Wheel 4 includes square teeth and spaces between them that are approximately equal. Element 3 has a size approximately the width of a tooth. The tachometer further includes a permanent magnet 5 mounted concentrically within shell 6 to establish magnetic flux from the teeth of wheel 4 to shell 6.

As each tooth passes element 3, the magnetic flux travelling from the tooth through the air gap passes through element 3 developing an applied voltage in accordance with Hall phenomena. The flux diminishes as the open tooth space approaches. A consecutive flux wave and consequently a waveshaped Hall voltage with a frequency equal to the number of teeth time the revolution of the cogged wheel or motor to which it is coupled is derived. A portion of the slope of this waveform is used in a single-shot transistor circuit to feed back a voltage to the motor in direct relation to its instantaneous speed as in C. The arrangement holds the motor at a predetermined steady speed independent of its supply voltage and l...