Circuit for enhancing resolution in tachometer signals

• US 3,909,717 A
• Filed: 04/22/1974
• Issued: 09/30/1975
• Est. Priority Date: 06/18/1973
• Status: Expired due to Term

• Current Assignee: Donald J. Gazzano
• Original Assignee: Donald J. Gazzano
• Inventors: Gazzano, Donald J.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Hille, Rolf
• Application Number:
  US05/462,898
• Time in Patent Office: 526 Days
• Field of Search: 324/161,166,173,174,175,78D,78F,78J,82 328/20,28,29,31,32,38,140,150 307/261,271,290,22R,225R,235R
• US Class Current: 324/166
• CPC Class Codes: G01P 3/48 by measuring frequency of generated current or voltage in general G01R23/00
• CPC Class Codes: H03D 3/04 by counting or integrating cycles of oscillations arrangements for measuring frequencies G01R23/10

Abstract

Tachometer signal resolution is enhanced by generating in phase and opposite sign representations of the signal and employing the representations in the detection of the zero axis crossovers in the signal to achieve frequency doubling. An additional enhancement capability is obtainable by preliminarily processing the tachometer signal through one or more frequency compressors.

Claims

1. A circuit for enhancing the resolution of a tachometer signal whose magnitude sinusoidally varies about an axis by determining the axis crossovers, comprising:

a means for generating two in phase representations of said sinusoidally varying signal with one of said representations inverted in sign with respect to the other;

a dual branch circuit, one of said representations being introduced to each of said branches, each branch of said circuit comprising a means for generating a pulse representative of a selected portion of the cycle of said representation introduced therein, said selected portion represented by the pulse generated by said means of one branch occurring at a time different from the occurrence of the selected portion represented by the pulse generated by the means of the other branch; and

means for receiving said pulses from said dual brancHes and responsive to each pulse representative of a selected portion of the cycle to initiate the generation of a signal and to the following pulse representative of another selected portion of the cycle to terminate the generation of said signal and thereby produce a signal representative of the axis crossovers of said sinusoidally varying signal.

2. A circuit in accordance with claim 1 wherein said means for generating representations of said sinusoidally varying signal is a differential amplifier with a two mode inverted output, said means for generating a pulse representative of a portion of said representation of said sinusoidally varying signal is a schmitt trigger, and said receiving means is a NAND gate.

3. A circuit in accordaance with claim 2 wherein low pass filters are inserted between the respective outputs of said differential amplifier and each of said schmitt triggers.

4. A circuit in accordance with claim 3 wherein lower trigger points on said schmitt triggers are placed at negativegoing axis crossovers and upper trigger points on said schmitt triggers are placed slightly above positive going axis crossovers.

5. A circuit in accordance with claim 4 in combination with at least one frequency compressor for accomplishing a preliminary frequency multiplication prior to said operation to produce the signal representation of said axis crossovers.

6. A circuit in accordance with claim 5 wherein two frequency compressors are employed.

7. A circuit in accordance with claim 6 wherein said frequency compressors comprise a dual branch circuit, each of said branches consisting, in order, of a diode, said diodes being inserted in their respective branches in inverted order with respect to each other, a resistor interconnected between each branch and ground and a capacitor, the output of said branches being introduced to a differential amplifier with a two mode inverted output so that the outputs of said amplifier represent a doubling of the frequency of the signal introduced to said dual branch circuit, the frequency compressor which is connected to said low pass filters producing said representations by taking the respective outputs from said differential amplifier of the other frequency compressor.

8. A circuit for enhancing the resolution of a tachometer signal that periodically varies about an axis by determining axis crossovers, comprising:

means for generating two in phase representations of said tachometer signal with one of said representations inverted in sign with respect to the other;

a first pulse generator means connected to receive one of said in phase representations and responsive each time said one representation crosses through its axis in a selected direction to generate a first pulse of a duration less than the interval between said axis crossover and the following axis crossover of said representation;

a second pulse generator means connected to receive the other of said in phase representations and responsive each time said other representation crosses through its axis in said selected direction to generate a second pulse of a duration less than the inverval between said axis crossover and the following axis crossover of said other representation; and

means responsive to the time relationship of each pulse generated by a pulse generator means and following pulse generated by the other pulse generating means to generate a signal representative of the axis crossover of said periodically varying tachometer signal.

9. A circuit in accordance with claim 8 wherein said first pulse generator means is responsive to each of the one representations to initiate the generation of the first pulse at a predetermined time after said one representation crosses its axis in the selected direction and to terminate the generation of said first pulse in response to said one representation next crossing its axis in a direction opposite said selected direction;

said second pulse generator means is responsive to the other reprEsentation to initiate the generator of the second pulse at a predetermined time after said other representation crosses its axis in said selected direction and to terminate the generation of said second pulse in response to said other representation next crossing its axis in a direction opposite said selected direction; and

the time relationship responsive means is responsive to each initiating edge of each of said first and second pulses and the following terminating edge of the other of said first and second pulses to generate a pulse as the axis crossover representative signal.

10. A circuit in accordance with claim 1 wherein each of said two in phase representations in a sinusoidal signal varying about an axis, each of said pulse generating means is responsive to the sinusoidal signal representation introduced therein to initiate the generation of a pulse at a predetermined time after said representation crosses said axis in a selected direction and to terminate the generation of said pulse in response to said representation next crossing said axis in a direction opposite said selected direction, and said means for receiving said pulses from said dual branches is responsive to a selected one of the edges of each pulse from a branch and the other edge of the following pulse from another branch to generate a pulse signal representative of the axis crossovers of said sinusoidally varying signal.