Browse Prior Art Database

Tachometer Circuits

IP.com Disclosure Number: IPCOM000076091D
Original Publication Date: 1972-Jan-01
Included in the Prior Art Database: 2005-Feb-24
Document File: 3 page(s) / 47K

Publishing Venue

IBM

Related People

Heussmann, DW: AUTHOR

Abstract

In precision measuring systems having two-phase tachometers, it is extremely important that glitch-free operations be provided. Each and every slight movement past a reference transition in either of the phases must be detected, such that location and direction of motion are faithfully tracked.

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Tachometer Circuits

In precision measuring systems having two-phase tachometers, it is extremely important that glitch-free operations be provided. Each and every slight movement past a reference transition in either of the phases must be detected, such that location and direction of motion are faithfully tracked.

Two-phase tachometer 10 supplies 90 degrees phase-displaced A and B pulses indicating relative displacement, velocity, and direction of motion of a motive system, either of a rotary or reciprocating type. The A pulses, or squarewaves, are processed by circuits 11; while the B pulses are processed by circuits 12. These circuits detect transitions and, under control of clock 13, effect indicating signals to direction detector and counter 14 for indicating direction of motion upon each and every transition detected in the A and B pulses and the amount of displacement, in accordance with selected transitions in the A pulses, all transitions in the A pulses, or transitions in both the A and B pulses. The periodicity of clock 13 is extremely short with respect to the periodicity of the A and B pulses. For improved synchronization between circuits 11, 12, and 14, clock 13 supplies a low-frequency clock signal (LOCLK) and a high-frequency clock signal (HICLK), which is preferably an integral multiple of the LOCLK pulse repetitive frequency.

Since phase A and phase B circuits 11 and 12 are constructed substantially identically, only the phase A circuits are described in detail. Two control latches C1L and C2L track the polarity of the A signal in a fashion that the transitions are faithfully detected and, under control of clock 13 signals, reliably set and reset SL latch 32. This latch determines the time when the direction of motion is detected,
i.e., when the polarities of A and B are compared. SL 32 supplies actuating signals to direction detector and counter 14.

Transition 20 resets C1L. SL 32 is set to the active condition upon the first- occurring positive transition of LOCLK, indicating circuits 14 are to make a direction determination. SL 32 actuates direction detector 14 to determine direction of motion. SL 32 enables an AND circuit, not shown, within detector 14 which then initiates the comparison in a known manner.

Counter 22 counts the number...