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Position Tachometer

IP.com Disclosure Number: IPCOM000046009D
Original Publication Date: 1983-May-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 54K

Publishing Venue

IBM

Related People

Haunsperger, MJ: AUTHOR

Abstract

In a digital position tachometer, a single, circular data track, containing N pulses, provides one unique start-of-track index pulse, as well as N-l evenly spaced emitter pulses, all of which comprise a position clock. More specifically, the unique start-of-track pulse (pulse N) is actually an emitter pulse which is unevenly spaced from the prior emitter pulse (N-1). As a result, N (for example, 1800) pulses are produced by one revolution of the tachometer, and yet a unique tachometer position (start of track) is also indicated.

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Position Tachometer

In a digital position tachometer, a single, circular data track, containing N pulses, provides one unique start-of-track index pulse, as well as N-l evenly spaced emitter pulses, all of which comprise a position clock. More specifically, the unique start-of-track pulse (pulse N) is actually an emitter pulse which is unevenly spaced from the prior emitter pulse (N-1). As a result, N (for example, 1800) pulses are produced by one revolution of the tachometer, and yet a unique tachometer position (start of track) is also indicated.

The above-mentioned circular data track is written onto a floppy magnetic recording disk under the control of the circuit of Fig. 1.

The disk is rotated by a motor. A tachometer is hard-coupled to the motor, and this tachometer issues (1) an emitter pulse for each (360/N)OE rotation of the motor, and (2) an index pulse, or startof-- track pulse, which occurs but once for each 360OE rotation of the motor. A write-head cooperates with the spinning disk, and so long as the "write gate" line of Fig. 1 is active, the tachometer's emitter pulses are "mapped" onto the disk by the write-head, as this head is energized by Fig. 1's "write data" line.

Fig. 2 shows the time relationship of the various signals shown in Fig. 1.

Single-shot l0 of Fig. 1 operates to turn on and off the write gate signal, i.e., enable the head to respond to the "write data" line, as shown by the arrow of Fig.
2.

When the positive-going edge 11 of the tachometer's index pulse is sensed, single-shot 10 operates, and a very short time thereafter Fig. 2's "write gate" signal becomes active. Thereafter, the tachometer's emitter signals are "mapped" onto the dis...