Battery tach
First Claim
1. A circuit for providing an output signal representative of speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the circuit comprising:
- means for deriving directly from the battery an input signal representative of time-varying components in battery current, where battery current is the current flow appearing at a battery terminal;
means for filtering the input signal to produce a filtered signal comprising time-varying components of the input signal having frequencies within a range of frequencies associated with a time-varying signal impressed upon the battery current by operation of the ignition system; and
means for suppressing components in the filtered signal not associated with ignition system operation to produce the output signal as a function of engine speed.
6 Assignments
0 Petitions
Accused Products
Abstract
A signal representing the RPM of an internal combustion engine is produced by a signal processor connected to the battery of the vehicle. The signal processor derives an electrical signal from the battery which contains signal components produced by operation of the vehicle ignition system, as well as components from a multitude of other sources such as the voltage regulator, fans, air conditioning and other electrical systems of the vehicle. The signal processor filters and signal processes the signal derived from the vehicle battery to produce a signal having a frequency which is related to the RPM of the engine.
237 Citations
29 Claims
-
1. A circuit for providing an output signal representative of speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the circuit comprising:
-
means for deriving directly from the battery an input signal representative of time-varying components in battery current, where battery current is the current flow appearing at a battery terminal; means for filtering the input signal to produce a filtered signal comprising time-varying components of the input signal having frequencies within a range of frequencies associated with a time-varying signal impressed upon the battery current by operation of the ignition system; and means for suppressing components in the filtered signal not associated with ignition system operation to produce the output signal as a function of engine speed. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
-
-
10. A method of measuring speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the method comprising:
-
deriving directly from the battery an input signal representative of battery current; filtering from the input signal representative of battery current, a time-varying signal including components associated with operation of the electrical ignition system, where battery current is current flow appearing at a battery terminal; and suppressing noise components of the time-varying signal to produce an output signal as a function of engine speed. - View Dependent Claims (11, 12, 13)
-
-
14. A circuit generating a tachometric output signal derived from electrical signals occurring in an electrical system for an internal combustion engine, the electrical system including a battery and an ignition system, the circuit comprising:
-
means for deriving directly from the battery an input signal representative of time-varying components in battery current, where battery current is the current flow appearing at a battery terminal; filtering means for attenuating components of the input signal having frequencies outside a predetermined range to produce a filtered signal; and means for suppressing noise in the filtered signal to produce the tachometric output signal.
-
-
15. A electronic tachometer responsive to signals occurring in an electrical system of an internal combustion engine, wherein the electrical system includes a battery and an ignition system which includes at least a first spark plug, the tachometer comprising:
-
means for deriving an input signal representative of time-varying components in battery current appearing at a battery terminal; a first signal processing path for generating a first tachometric output signal from time-varying components of the input signal associated with primary switching current in the ignition system; a second signal processing path for generating a second tachometric output signal from time-varying components of the input signal associated with ignition burst spark plug ringing; and means for selecting between the first and second tachometric output signals; and means responsive to the selected tachometric output signal for displaying engine rotational speed. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
-
-
23. A electronic tachometer operating on signals occurring in an electrical system for an internal combustion engine, wherein the electrical system includes a battery and an ignition system which includes at least a first spark plug, the tachometer comprising:
-
input terminals for connection to positive and negative terminals of the battery for developing an input signal representative of time-varying components in battery current; a first signal processing path for generating a first tachometric output signal from components of the input signal associated with primary switching current, the first signal processing path including, filtering means for attenuating components of the input signal having frequencies outside predetermined frequency ranges and producing filtered signals associated with each frequency range; means for selecting a filtered signal; and a noise suppression stage including, means for generating set and reset signals in response to transitions of the selected filtered signal exceeding threshold levels, and a bistable device responsive to the set and reset signals for producing a first tachometric output signal; a second signal processing path for generating a second tachometric output signal from components of the signal associated with ignition burst spark plug ringing, the second signal processing path comprising, filtering means for attenuating components of the input signal having frequencies outside a predetermined frequency range and producing a filtered signal; and a spark plug ring detect stage operating on the filtered signal, the ring detect stage including, a fast peak detector operating on the filtered signal, a sloe peak detector operating on the filtered signal, and means for comparing outputs of the fast and slow peak detectors for producing the tachometric output signal; means for selecting between the first and second tachometric output signals; and means responsive to the selected tachometric output signal for displaying engine rotational speed.
-
-
24. A electronic tachometer operating on signals occurring in an electrical system for an internal combustion engine, wherein the electrical system includes a battery and an ignition system, the tachometer comprising:
-
means for deriving an input signal representative of time-varying components in battery current; a signal processing path for generating a tachometric output signal from components of the input signal associated with primary switching current, the signal processing path including, filtering means for attenuating components of the input signal having frequencies outside predetermined frequency ranges and producing filtered signals associated with each frequency range; means for selecting between filtered signals; and a noise suppression stage including, means for generating set and reset signals in response to transitions of the selected filtered signal exceeding threshold levels, and a bistable device responsive to the set and reset signals for producing a first tachometric output signal; and means for displaying engine rotational speed in response to a tachometric signal.
-
-
25. A electronic tachometer operating on signals occurring in an electrical system for an internal combustion engine, wherein the electrical system includes a battery and an ignition system which includes at least a first spark plug, the tachometer comprising:
-
means for deriving an input signal representative of time-varying components in battery current; a signal processing path for generating a tachometric output signal from components of the input signal associated with spark plug ringing, the signal processing path comprising, filtering means for attenuating components of the representative signal having frequencies outside a predetermined frequency range and producing a filtered signal; and a spark plug ring detect stage operating on the filtered signal, the ring detect stage including; a fast peak detector operating on the filtered signal; a slow peak detector operating on the filtered signal; and means for comparing outputs of the fast and slow peak detectors for producing the tachometric output signal; means for displaying engine rotational speed in response to a tachometric signal.
-
-
26. A circuit for providing a tachometric output signal representative of speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the circuit comprising:
-
first connector means for making direct and continuous electrical connection to a positive terminal of the battery; a second connector means for making direct and continuous electrical connection to a negative terminal of the battery; means connected to the first and second connector means for deriving an electrical signal from the battery which includes DC and AC components; means for removing the DC component from the electrical signal; means for processing the AC components of the electrical signal to select one of the AC components which is representative of operation of the ignition system and which changes as a function of engine speed; and means for producing the tachometric output signal as a function of the AC component selected.
-
-
27. A circuit for providing a tachometric output signal representative of speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the circuit comprising:
-
means for making direct and continuous electrical connection to positive and negative terminals of the battery to derive from the battery a multi-component electrical signal appearing across the positive and negative terminals, wherein the electrical signal contains DC and AC components; means for separating from the multi-component electrical signal an AC signal component produced by primary switching current of the ignition system; and means for producing the tachometric output signal as a function of the AC signal component produced by primary switching current of the ignition system.
-
-
28. A circuit for providing a tachometric output signal representative of speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the circuit comprising:
-
means for making direct and continuous electrical connection to positive and negative terminals of the battery to derive from the battery a multi-component electrical signal appearing across the positive and negative terminals, wherein the electrical signal contains DC and AC components; means for separating from the multi-component signal an AC signal component produced by spark plug ringing in the ignition system; and means for producing the tachometric output signal as a function of the AC signal component produced by spark plug ringing in the ignition system.
-
-
29. A circuit for providing an output signal representative of speed of an internal combustion engine of the type having an electrical ignition system connected to a battery, the circuit comprising:
-
means for deriving an input signal representative of time-varying components in battery current, where battery current is the current flow appearing at a battery terminal; means for filtering the input signal to produce a filtered signal comprising time-varying components of the input signal having frequencies within a range of frequencies associated with a time-varying signal impressed upon the battery current by operation of the ignition system, wherein the means for filtering attenuates time-varying components having a frequency outside a range of frequencies normally associated with primary ignition current pulses to extract a first time-varying component related to engine speed and wherein the means for filtering comprises; first filter means for attenuating signals with frequencies outside a first range associated with primary ignition current pulses produced by the ignition system when the engine is idling; second filter means for attenuating signals with frequencies outside a second range associated with primary ignition current pulses produced by the ignition system when the engine is revving; means for selecting a signal from one of the first and second filter means as a function of engine speed; and means for suppressing components in the filtered signal not associated with ignition system operation to produce the output signal as a function of engine speed.
-
Specification