Digital photo-optical tachometer

• US 4,031,466 A
• Filed: 05/05/1975
• Issued: 06/21/1977
• Est. Priority Date: 05/05/1975
• Status: Expired due to Term

• Current Assignee: The Pioneer Electric and Research Corporation
• Original Assignee: The Pioneer Electric and Research Corporation
• Inventors: Krause, Ernest Harry, Angelopoulos, Peter Gregory, Seaman, Wesley Arthur
• Primary Examiner(s): Rolinec, Rudolph V.
• Assistant Examiner(s): Sunderdick, Vincent J.
• Application Number:
  US05/574,252
• Time in Patent Office: 778 Days
• Field of Search: 324/166, 324/168, 324/175, 324/169, 324/79 R, 324/82, 324/83 R, 324/83 FE, 340/262
• US Class Current: 324/175
• CPC Class Codes: G01P 3/489 Digital circuits therefor

Abstract

A digital tachometer having an optical sensor which provides a signal at a frequency related to the rotational or reciprocating speed of a moving object, a phase locked loop and a frequency divider circuit connected for operation as a frequency multiplier to be responsive to the sensor signal to provide a serial pulse train the period of which is an integral multiple of the sensor signal, a pulse accumulator for registering the pulses and a time rate generator which enables the pulse accumulator to register pulses for a preset duration so that the number of pulses registered is a direct representation of the revolutions per minute of the moving object.

Claims

1. In a tachometer for measuring the rotational or reciprocating speed of a moving object, the combination comprising sensing means for deriving an input signal related in frequency to the speed of the object, frequency detecting means including phase comparator means for comparing said input signal with a reference signal of a predetermined frequency and for providing a series of output pulses having a frequency which is an integral multiple of the frequency of the input signal, timing means, and output means controlled by said timing means to be responsive to the number of output pulses provided within a predetermined time duration to provide an indication of the speed of said object.

2. A tachometer as set forth in claim 1 which includes range select means for selecting the reference signal to thereby permit the determination of the rotational speed of said rotating object to be measured over a predetermined number of ranges.

3. In a tachometer for measuring the rotational or reciprocating speed of a moving object, the combination comprising sensing means for deriving an input signal related in frequency to the speed of the object, frequency detecting means including phase comparator means for comparing said input signal with a reference signal of a predetermined frequency, said phase comparator means including a phase locked loop means having an input connected to said sensing means to receive said input signal and to be responsive to said input signal to provide a series of output pulses, the frequency of which is related to the frequency of the input signal, timing means, and output means controlled by said timing means to be responsive to the number of pulses provided within a predetermined time duration to provide an indication of the speed of said object, said phase locked loop means having an output connected over said timing means to said output means, to permit said pulses to be supplied to said output means under the control of said timing means.

4. A tachometer as set forth in claim 3 wherein said phase locked loop means includes frequency divider means for controlling said phase locked loop means to provide a serial pulse train output, the period of which is an integral multiple of the input signal as determined by said frequency divider means.

5. A tachometer as set forth in claim 4 wherein said phase locked loop means includes reference means for providing said reference signal, and range select means for enabling said reference means to provide a reference signal of a different predetermined frequency for each of a predetermined number of ranges to thereby permit the determination of the rotational speed of said rotating object to be measured over said predetermined number of ranges.

6. A tachometer as set forth in claim 4 wherein said output means includes pulse accumulator means operable to store each pulse extended thereto during said predetermined time, said timing means including means for preventing pulses from being extended to said pulse accumulator means during a second predetermined time duration following said first predetermined time duration.

7. A tachometer as set forth in claim 6 wherein said output means further includes indicator means comprising a digital display means, said pulse accumulator means providing digital coded output signals to said digital display means to effect the display of data representing the rotational speed of said object during said second predetermined time duration.

8. In a tachometer for measuring the rotational or reciprocating speed of a moving object, the combination comprising sensing means including a photo-optical sensor having a light source means and a light detecting means for deriving an input signal related in frequency to the speed of the object, frequency detecting means including phase comparator means for comparing said input signal with a reference signal of a predetermined frequency and for providing a series of output pulses the frequency of which is related to the frequency of the input signal, timing means, and output means controlled by said timing means, to be responsive to the number of pulses provided within a predetermined time duration to provide an indication of the speed of said object.

9. In a tachometer for measuring the rotational or reciprocating speed of a moving object, the combination comprising photo-optical sensing means for providing an input signal related in frequency to the speed of the object, frequency detecting means including a phase locked loop means including means for providing a reference signal of a predetermined frequency and means for comparing said reference signal with said input signal, said phase locked loop means being operable to provide a series of pulses, the period of which is related to the frequency of the input signal, pulse accumulator means, timing means for enabling said pulses to be extended to said pulse accumulator means, said pulse accumulator means including means for registering the pulses extended thereto, said timing means including clock pulse generating means for establishing a first time period of a preset duration during which said pulses are extended to said pulse accumulator means and a second time period of a preset duration, following said first time period, during which pulses are prevented from being extended to said pulse accumulator means whereby the number of pulses registered by said pulse accumulator means represents the speed of said object, and indicator means controlled by said pulse accumulator means to provide a display of numerical data indicative of the speed of said object.

10. A tachometer as set forth in claim 9 wherein said frequency detecting means includes frequency divider means for controlling said phase locked loop means to provide a serial pulse train the frequency of which is a preset integral multiple of the frequency of the input signal.

11. A tachometer as set forth in claim 9 wherein said timing means further includes gating means interposed between an output of said phase locked loop means and an input of said pulse accumulator means, and operable when enabled to extend said pulses to said pulse accumulator means, said clock pulse generating means operable to provide a first timing signal of said preset duration for enabling said gating means for said first time period and operable to provide a second timing signal of said preset duration for disabling said gating means for said second time period.

12. A tachometer as set forth in claim 11 wherein said clock pulse generating means includes oscillator means for providing a signal of a predetermined frequency, and frequency counting means responsive to said frequency signal to provide said first and second timing signals.

13. A tachometer as set forth in claim 12 wherein said gating means includes means for providing a reset signal for said frequency counting means after said first predetermined period to enable said frequency counting means to provide said second timing signal.

14. A tachometer as set forth in claim 12 wherein said oscillator means comprises a crystal oscillator.

15. A tachometer as set forth in claim 9 wherein said indicator means comprises a plurality of segmented light emitting diode display means each individually controlled by said pulse accumulator means to provide a digital display of said numerical data.