Tachometer without physical connection to internal combustion engine
First Claim
1. A tachometer for internal combustion engines, comprising,a transducer for translating a pressure waveform emitted by the engine to a corresponding electrical signal having a prominent frequency component which varies in frequency in direct proportion with engine speed,an amplifier for said signal including automatic gain control means, anda tracking filter receptive to the output of said amplifier and having a frequency pass band which tracks and passes said prominent frequency component as the frequency changes due to changes in engine speed,whereby the output of said tracking filter is an electrical wave having a frequency representing engine speed.
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Abstract
A tachometer includes a transducer for sensing pressure variations at the end of the exhaust pipe, or other easily-accessible point, due to explosions in an internal combustion engine. The transducer produces a corresponding electrical signal having a prominent selected frequency component which varies in frequency in direct proportion with engine speed. As the engine speed is increased and decreased, the electrical signal is passed through an amplifier with automatic gain control, and through a tracking filter to separate the prominent frequency component from other components. The separated component may be applied to a frequency-measuring device calibrated to display the revolutions per minute of the engine, or to a computer which computes and displays the result of an acceleration burst test.
17 Citations
8 Claims
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1. A tachometer for internal combustion engines, comprising,
a transducer for translating a pressure waveform emitted by the engine to a corresponding electrical signal having a prominent frequency component which varies in frequency in direct proportion with engine speed, an amplifier for said signal including automatic gain control means, and a tracking filter receptive to the output of said amplifier and having a frequency pass band which tracks and passes said prominent frequency component as the frequency changes due to changes in engine speed, whereby the output of said tracking filter is an electrical wave having a frequency representing engine speed.
Specification