A PIEZO-ELECTRIC METHOD OF MEASURING THE PRESSURE VARIATIONS IN INTERNAL COMBUSTION ENGINES

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Abstract
A piezo-electric pressure gauge is described in which the pressures produced by the explosions in an internal combustion engine are recorded as the displacements of the beam of a cathode-ray oscillograph. By applying a time displacement, synchronizing with the speed of the engine, to the beam so as to cause a displacement at right angles to the pressure displacements, the time-pressure characteristics of the engine explosions are obtained on a photographic film. This arrangement reduces the inertia of the gauge to a minimum and is of special value in obtaining records of a single cycle in the investigation of knocks. Specimen records taken on a Petter hot surface engine are given.