Tachometer
First Claim
1. A tachometer for measuring the speed of an engine, comprising:
- an inductive pickup disposed about a spark plug wire and operative to detect current pulses flowing through the spark plug wire and to generate pickup pulse signals in response thereto;
a counter circuit for counting the pulse signals generated by the inductive pickup;
a conversion circuit, including a plurality of lookup tables, each lookup table having mapped information for deriving and displaying engine speed information from the pickup pulse signals, the mapped information correlating pickup pulse signal frequency to engine speed information for a predetermined number of engine cylinders;
an automatic switching device, operative to sequentially access one of the lookup tables; and
a meter display operative to display the engine speed information.
2 Assignments
0 Petitions
Accused Products
Abstract
A tachometer used to measure a speed of an engine. The tachometer includes a pickup, a counter circuit, a conversion circuit, an automatic switching device, an indicator and a meter display. The inductive pickup may be disposed around a spark plug wire of the engine to generate a pulse signal in response to a current flowing through the spark plug wire. The pulse signals are then counted by the counter circuit and input to the conversion circuit therefrom. The conversion circuit typically includes a plurality of lookup tables, each having mapped information correlating the pulse signals to the engine speed for a particular number of engine cylinders. The automatic switching device is operative to call up alternate lookup tables, e.g. each time when the electrical system of the engine is turned on. The display may be display the number of engine cylinders called up by the automatic switching device and measured engine speed.
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Citations
22 Claims
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1. A tachometer for measuring the speed of an engine, comprising:
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an inductive pickup disposed about a spark plug wire and operative to detect current pulses flowing through the spark plug wire and to generate pickup pulse signals in response thereto;
a counter circuit for counting the pulse signals generated by the inductive pickup;
a conversion circuit, including a plurality of lookup tables, each lookup table having mapped information for deriving and displaying engine speed information from the pickup pulse signals, the mapped information correlating pickup pulse signal frequency to engine speed information for a predetermined number of engine cylinders;
an automatic switching device, operative to sequentially access one of the lookup tables; and
a meter display operative to display the engine speed information. - View Dependent Claims (2, 3, 4, 5)
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6. A tachometer operative for measuring the speed of an engine with a predetermined number of engine cylinders, the tachometer comprising:
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a connector, inserted to a terminal of a spark plug and a terminal of an ignition coil of an engine, the connector being operative to tap current spikes generated by the ignition coil, and to generate pickup pulse signals in response thereto;
a counter circuit for counting the pulse signals generated by the inductive pickup;
a conversion circuit, including a plurality of converting circuits each being operative to derive engine speed information from the pickup pulse signals, correlating the pickup pulse signals to engine speed information for a predetermined number of engine cylinders;
an automatic switching device, operative to select one of the converting circuits; and
a meter display, operative to display the engine speed information. - View Dependent Claims (7, 8, 9, 10, 11, 12)
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13. A tachometer for measuring the speed of an engine, comprising:
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an inductive pickup disposed about a spark plug wire and operative to detect current pulses flowing through the spark plug wire and to generate pickup pulse signals in response thereto;
a counter circuit for counting the pulse signals generated by the inductive pickup;
a conversion circuit, including a plurality of lookup tables, each lookup table having mapped information correlating pickup pulse signal frequency to engine speed information for a predetermined number of engine cylinders;
an automatic switching device, operative to sequentially access one of the lookup table;
a meter display operative to display the engine speed information; and
a filter coupled to the inductive pickup for filtering the pulse signals corresponding to exhaust sparks, the filter being operative to filter out pulse signals having a pulse width shorter than a predetermined length. - View Dependent Claims (14, 15)
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16. A tachometer operative for measuring the speed of an engine with a predetermined number of engine cylinders, the tachometer comprising:
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a connector, inserted to a terminal of a spark plug and a terminal of an ignition coil of an engine, the connector being operative to tap current spikes generated by the ignition coil, and to generate pickup pulse signals in response thereto;
a counter circuit for counting the pulse signals generated by the inductive pickup;
a conversion circuit, including a plurality of converting circuits each being operative to derive engine speed information from the pickup pulse signals, correlating the pickup pulse signals to engine speed information for a predetermined number of engine cylinders;
an automatic switching device, operative to select one of the converting circuits;
a meter display, operative to display the engine speed information;
a filter coupled to the inductive pickup for filtering out signals having a pulse width shorter then a predetermined length, the predetermined length being selected to distinguish exhaust sparks from ignition sparks. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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Specification