Wireless portable tachometer

• US 3,886,450 A
• Filed: 08/06/1973
• Issued: 05/27/1975
• Est. Priority Date: 08/06/1973
• Status: Expired due to Term

• Current Assignee: Gerald C. Trussell, James R. Caruth
• Original Assignee: Gerald C. Trussell, James R. Caruth
• Inventors: Trussell, Gerald C., Caruth, James R.
• Primary Examiner(s): Smith, Alfred E.
• Assistant Examiner(s): Hille, Rolf
• Application Number:
  US05/386,033
• Time in Patent Office: 659 Days
• Field of Search: 324/15,16R,165,169,170
• US Class Current: 324/170
• CPC Class Codes: G01P 3/4807 by using circuits for the detection of the pulses delivered by the ignition system of an internal combustion engine

Abstract

Apparatus for measuring the operating speed (RPM) of an internal combustion engine without attachment to the engine. The apparatus basically includes antenna input means having a resonant frequency for receiving the radiation signals emitted by the engine with each spark plug firing and for generating a resonating voltage signal in response to each radiation signal, tuning or filter means for passing frequencies within a bandwidth including the resonant frequency, amplitude detection means for discriminating the resonating voltage signal from accompanying noise and for generating a control pulse in response to each resonating signal, and output means for displaying the measured RPM in response to the control pulse repetition rate.

Claims

1. Apparatus for measuring the rate of operation of an internal combustion engine which emits valid electromagnetic radiation signals at a repetition rate corresponding to the rate of operation, comprising, in combination:

antenna input means having a predetermined resonant frequency for producing in response to each of the radiation signals a resonant signal at the resonant frequency having a positive voltage amplitude peak and a negative voltage amplitude peak;

valid signal detection means for generating a control pulse in response to each resonant signal having a positive voltage amplitude peak greater than a predetermined voltage, a negative voltage amplitude peak less than a second predetermined voltage and a time period between the positive and negative voltage amplitude peaks less than a predetermined time so that valid electromagnetic radiation signals are distinguished from noise signals; and

output means responsive to the repetition rate of the control pulses for indicating the rate of operation of the engine.

2. Apparatus, as claimed in claim 1, wherein the antenna input means comprises a tunable tank circuit.

3. ApParatus, as claimed in claim 1, wherein the predetermined resonant frequency is within the range of 5 kilohertz to 30 kilohertz.

4. Apparatus, as claimed in claim 3, wherein the predetermined resonant frequency is about 10 kilohertz.

5. Apparatus, as claimed in claim 1, wherein the valid signal detection means comprises filter means for passing a predetermined band of frequencies including the predetermined resonant frequency and for attenuating all frequencies outside the predetermined band.

6. Apparatus, as claimed in claim 1, wherein the valid signal detection means comprises:

first voltage level discriminator means for commencing the production of a first output pulse at the time the positive voltage amplitude peak of the resonant signal becomes greater than the first predetermined voltage and for continuing the production of the first output pulse for a first predetermined time interval;

second voltage level discriminator means for commencing the production of a second output pulse at the time the negative voltage amplitude peak of the resonant signal becomes less than the second predetermined voltage and for continuing the production of the second output pulse for a second predetermined time interval; and

coincidence means for producing the control pulse in response to the simultaneous production of the first output pulse and the second output pulse.

7. Apparatus, as claimed in claim 6, wherein the first predetermined time interval is between one quarter and three quarters of the period of time defined by the inverse of the predetermined resonant frequency.

8. Apparatus, as claimed in claim 1, wherein the valid signal detection means comprises blanking means for blanking said valid signal detection means for a predetermined time interval.

9. Apparatus, as claimed in claim 8, wherein the blanking means comprises means for extending the duration of the control pulse for the predetermined time interval.

10. Apparatus, as claimed in claim 1, wherein the output means comprises:

signal generator means for producing a meter signal in response to each control pulse;

adjustment means for varying the duration of the meter signals according to the characteristics of the internal combustion engine; and

a meter for indicating the rate of operation of the internal combustion engine in response to the duration and repetition rate of the meter signals.

11. In a system including an internal combustion engine operated by a plurality of spark discharge devices fired by current pulses producing electromagnetic radiation pulses, apparatus for measuring the operating speed of the engine, comprising:

antenna means for converting the radiation pulses into corresponding electrical signals;

tunable means for passing the electrical signals from the antenna means having frequencies in the audio range and for attenuating the electrical signals from the antenna means having frequencies outside the audio range;

valid signal detection means for generating a control pulse in response to the passed electrical signals having an amplitude exceeding a predetermined value and having a period less than a predetermined time interval; and

output means responsive to the repetition rate of the control pulses for indicating the operating speed of the engine.

12. Apparatus, as claimed in claim 11, wherein the tunable means comprises tank circuit means connected to the antenna means and having a resonant frequency in the audio range for producing a series of decaying resonant signals in response to each radiation pulse received by the antenna means.

13. Apparatus, as claimed in claim 12, wherein the resonant frequency is within the range of 5 kilohertz to 30 kilohertz.

14. Apparatus, as claimed in claim 13, wherein the predetermined resonant frequency is about 10 kilohertz.

15. Apparatus, as claimed in claim 11, wherein the tunable means comprises filter means for attenuating all frequenCies outside a predetermined frequency band.

16. Apparatus, as claimed in claim 11, wherein the output means comprises:

signal generator means for producing a meter signal in response to each control pulse;

adjustment means for varying the duration of the meter signals according to the characteristics of the internal combustion engine; and

a meter for indicating the speed of the internal combustion engine in response to the duration and repetition rate of the meter signals.

17. Apparatus, as claimed in claim 11, wherein the antenna means is electromagnetically coupled to the engine along an unobstructed straight-line path through the atmosphere.

18. Apparatus for measuring the operating speed of an internal combustion engine operated by a plurality of spark discharge devices fired by current pulses producing electromagnetic radiation pulses, comprising, in combination:

antenna means for converting the radiation pulses into corresponding electrical signals;

tunable means for passing the electrical signals from the antenna means having frequencies in the audio range and for attenuating the electrical signals from the antenna means having frequencies outside the audio range;

valid signal detection means for generating a control pulse in response to the passed electrical signals having an amplitude exceeding a predetermined value and having a period less than a predetermined time interval; and

output means responsive to the repetition rate of the control pulses for indicating the operating speed of the engine.

19. Apparatus, as claimed in claim 18, wherein the tunable means comprises tank circuit means connected to the antenna means and having a resonant frequency in the audio range for producing a series of decaying resonant signals in response to each radiation pulse received by the antenna means.

20. Apparatus, as claimed in claim 19, wherein the predetermined resonant frequency is within the range of 5 kilohertz to 30 kilohertz.

21. Apparatus, as claimed in claim 20, wherein the predetermined resonant frequency is about 10 kilohertz.

22. Apparatus, as claimed in claim 18, wherein the tunable means comprises filter means for attenuating all frequencies outside the predetermined frequency band.

23. Apparatus, as claimed in claim 18, wherein the output means comprises:

signal generator means for producing a meter signal in response to each control pulse;

adjustment means for varying the duration of the meter signals according to the characteristics of the internal combustion engine; and

a meter for indicating the speed of the internal combustion engine in response to the duration and repetition rate of the meter signals.

24. Apparatus, as claimed in claim 18, wherein the antenna means is electromagnetically coupled to the engine along an unobstructed straight line path through the atmosphere.

25. A method for measuring the rate of operation of an internal combusion engine having an ignition system, the ignition system intermittently emitting a series of electromagnetic radiation signals at a rate proportional to the rate of operation, comprising, in combination, the steps of:

receiving the electromagnetic radiation signals;

developing a voltage signal having an amplitude peak in response to the radiation signals;

attenuating all signals having a frequency outside the upper sonic range;

generating a control pulse whenever the amplitude peaks of two successive voltage signals exceed a predetermined value and the period between the two successive voltage signals is less than a predetermined time period; and

displaying in response to the repetition rate of the control pulses the rate of operation.

26. The method of claim 25 including between the attenuating step and the generating step the additional step of comparing the amplitude peak to the predetermined value.

27. A method for measuring by means of an aNtenna having a resonant frequency in the audio range, the rate of operation of an internal combustion engine having an ignition system, the ignition system intermittently emitting a series of electromagnetic radiation signals at a rate proportional to the rate of operation, comprising, in combination, the steps of:

placing the antenna in the vicinity of the engine;

receiving the electromagnetic radiation signals;

developing a resonating voltage signal having an amplitude peak in response to each radiation signal;

attenuating all signals having a frequency outside the audio range;

generating a control pulse whenever the amplitude peaks of two successive voltage signals exceed a predetermined value and the period between the two successive voltage signals is less than a predetermined time period; and

displaying in response to the repetition rate of the control pulses the rate of operation.

28. The method of claim 27 wherein the resonant frequency is in the range of 5 kilohertz to 30 kilohertz.

29. The method of claim 28 wherein the resonant frequency is approximately 10 kilohertz.