Tachometer based on electrical ripple and calibrated by mechanical engine signals
First Claim
1. A tachometer for determining the speed of the engine in a vehicle that includes a battery-operated electrical system which produces a DC voltage having a ripple thereon, the engine producing mechanical oscillations during operation, the tachometer comprising:
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple, a second input circuit for coupling to the engine for providing second signals representative of the frequency of the mechanical oscillations, and a processing circuit coupled to said first and second input circuits and operating under stored program control for calculating a constant representing the relationship of the frequencies of the first and second signals and for responding to said first signals and the constant to provide third signals corresponding to the speed of the engine.
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Accused Products
Abstract
The tachometer includes a microphone for disposition next to the exhaust of the vehicle and an accelerometer for disposition adjacent to its engine. A selected one of the outputs is connected to an ADC which provides digital samples to a central processing unit. Also, the ripple from the battery is sampled and provided to the CPU. The CPU calculates a constant representing the relationship of the frequencies of the ripple samples and the mechanical samples and responds to the ripple samples and the constant to provide output signals corresponding to the speed of the engine. The speed is displayed.
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Citations
20 Claims
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1. A tachometer for determining the speed of the engine in a vehicle that includes a battery-operated electrical system which produces a DC voltage having a ripple thereon, the engine producing mechanical oscillations during operation, the tachometer comprising:
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple, a second input circuit for coupling to the engine for providing second signals representative of the frequency of the mechanical oscillations, and a processing circuit coupled to said first and second input circuits and operating under stored program control for calculating a constant representing the relationship of the frequencies of the first and second signals and for responding to said first signals and the constant to provide third signals corresponding to the speed of the engine.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A tachometer for determining the speed of the engine in a vehicle that includes a battery-operated electrical system which produces a DC voltage having a ripple thereon, the engine producing mechanical oscillations during operation, the tachometer comprising:
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple, a second input circuit for coupling to the engine for providing second signals representative of the frequency of the mechanical oscillations, an analog-to-digital converter coupled to said first and second means to provide ripple samples in response to the first signals and mechanical samples in response to the second signals, and a central processing unit coupled to said analog-to-digital converter and operating under stored program control for calculating a constant representing the relationship of the frequencies of the ripple samples and the mechanical samples and for responding to said ripple samples and the constant to provide output signals corresponding to the speed of the engine.
- View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A tachometer for determining the speed of the engine in a vehicle that includes a battery-operated electrical system which produces a DC voltage having a ripple thereon, the engine producing mechanical oscillations during operation, the tachometer comprising:
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple;
a second input circuit for coupling to the engine for providing second signals representative of the frequency of the mechanical oscillations; and
a central processing unit coupled to said input circuits and operating under stored program control for (a) calculating the frequency of the ripple, (b) calculating the frequency of the mechanical oscillations to provide a mechanical frequency and storing the calculated mechanical frequency and repeating this calculation and storage step a predetermined number of times, (c) averaging the calculated and stored mechanical frequencies to provide a representative mechanical frequency, (d) calculating a constant representing the relationship of the frequency of the ripple and the representative mechanical frequency, and (e) responding to the constant and the frequency of the ripple to provide output signals corresponding to the speed of the engine.
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple;
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20. A tachometer for determining the speed of the engine in a vehicle that includes a battery-operated electrical system which produces a DC voltage having a ripple thereon, the engine producing mechanical oscillations during operation, the tachometer comprising:
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple;
a second input circuit for coupling to the engine for providing second signals representative of the frequency of the mechanical oscillations; and
a central processing unit coupled to said input circuits and operating under stored program control for (a) calculating the frequency of the ripple, (b) calculating the frequency of the mechanical oscillations to provide a mechanical frequency, (c) calculating the ratio of the mechanical frequency to the frequency of the ripple and storing the ratio and repeating this calculation and storage step a predetermined number of times to identify a representative ratio which becomes a constant, and (d) responding to the constant and the frequency of the ripple to provide output signals corresponding to the speed of the engine.
- a first input circuit for coupling to the electrical system for providing first signals representative of the frequency of the ripple;
Specification