Apparatus for measuring the dwell of an automotive ignition system

Claim 1

An apparatus for measuring the dwell of an ignition system having a primary ignition signal comprising, in combination: input means for receiving said primary ignition signal; conversion means for producing a modified primary ignition signal, representing the absolute value of said primary ignition signal; storage means for storing a voltage; controllably conductive means operable in a first state and a second state in response to said modified primary ignition signal, said controllably conductive means charging said storage means in said first state and discharging said storage means in said second state, said controllably conductive means defining a voltage threshold, said controllably conductive means being operable in said first state whenever said voltage threshold exceeds said modified primary ignition signal, said controllably conductive means being operable in said second state whenever said second modified primary ignition signal exceeds said voltage threshold; comparator means for comparing said voltage to a comparison voltage, said comparator means being operable in a first comparator state whenever said comparison voltage exceeds said voltage to produce a first output signal, said comparator means being operable in a comparator second state whenever said voltage exceeds said comparison voltage to produce a second output signal; means for setting said comparison voltage in response to said first output signal of said comparator means and said primary ignition signal, said comparison voltage being a positive voltage substantially throughout said first comparator state and a negative voltage substantially throughout said second comparator state; detector means for detecting a voltage crossing between said first output signal and said second output signal of said comparator means; and means for coupling said comparator means and said detector means, said coupling means including means for delaying transmission of said second output signal to said detector means whenever said comparator means switches from said first comparator state to said second comparator state, said detector means generating a signal in response to said comparator means representing said dwell of said ignition system.

Claim 2

An apparatus for measuring the dwell of an ignition system having a primary ignition signal comprising, in combination: input means for receiving said primary ignition signal; conversion means for producing a modified primary ignition signal, representing the absolute value of said primary ignition signal; storage means for storing a voltage; controllably conductive means operable in a first state and a second state in response to said modified primary ignition signal, said controllably conductive means charging said storage means in said first state and discharging said storage means in said second state, said controllably conductive means defining a voltage threshold, said controllably conductive means being operable in said first state whenever said voltage threshold exceeds said modified primary ignition signal, said controllably conductive means being operable in said second state whenever said second modified primary ignition signal exceeds said voltage threshold; comparator means for comparing said voltage to a comparison voltage, said comparator means being operable in a first comparator state whenever said comparison voltage exceeds said voltage to produce a first output signal, said comparator means being operable in a comparator second state whenever said voltage exceeds said comparison voltage to produce a second output signal; means for setting said comparison voltage in response to said first output signal of said comparator means and said primary ignition signal, said comparison voltage being a positive voltage substantially throughout said first comparator state and a negative voltage substantially throughout said second comparator state; detector means for detecting a voltage crossing between said first output signal and said second output signal of said comparator means; and means for coupling said comparator means and said detector means, said coupling means including means for delaying transmission of said second output signal to said detector means whenever said comparator means switches from said first comparator state to said second comparator state, said detector means generating a signal in response to said comparator means representing said dwell of said ignition system.

Claim 13

An apparatus for measuring the dwell of an ignition system producing a primary ignition signal, said primary ignition signal having peak and a dwell period, comprising, in combination: storage means for storing a voltage; controllably conductive means, operable in a first state and a second state, for charging said storage means in said first state and discharging said storage means in said second state, said controllably conductive means defining a voltage threshold, said controllably conductive means being responsive to said primary ignition signal and operable in said first state whenever said primary ignition signal is substantially within said voltage threshold or 0 volts; comparator means for comparing said voltage to a comparison voltage, said comparator means being operable in a first comparator state to produce a first output signal and operable in a second comparator state to produce a second output signal; means for setting said comparison voltage in said first and second comparator states, whereby said comparator means switches to said first comparator state a predetermined time after initiation of said dwell period and switches to said second comparator state in response to said peak; detector means for detecting a voltage crossing between said first output signal and said second output signal of said comparator means, said detector means producing an output signal in response to said voltage crossings; and delay means for delaying transmission of said second output signal to said detector means for substantially said predetermined time whenever said comparator means switches from said first comparator state to said second comparator state.

Claim 14

An apparatus for measuring the dwell of an ignition system producing a primary ignition signal, said primary ignition signal having peak and a dwell period, comprising, in combination: storage means for storing a voltage; controllably conductive means, operable in a first state and a second state, for charging said storage means in said first state and discharging said storage means in said second state, said controllably conductive means defining a voltage threshold, said controllably conductive means being responsive to said primary ignition signal and operable in said first state whenever said primary ignition signal is substantially within said voltage threshold or 0 volts; comparator means for comparing said voltage to a comparison voltage, said comparator means being operable in a first comparator state to produce a first output signal and operable in a second comparator state to produce a second output signal; means for setting said comparison voltage in said first and second comparator states, whereby said comparator means switches to said first comparator state a predetermined time after initiation of said dwell period and switches to said second comparator state in response to said peak; detector means for detecting a voltage crossing between said first output signal and said second output signal of said comparator means, said detector means producing an output signal in response to said voltage crossings; and delay means for delaying transmission of said second output signal to said detector means for substantially said predetermined time whenever said comparator means switches from said first comparator state to said second comparator state.