Piezoelectric Oscillograph. V. Filippov has designed a piezoelectric oscillograph consisting of two quartz plates measuring \(70 \times 20 \times 0.7\ \mathrm{mm}^3\) (the last dimension being in the direction of the electric axis of the crystal), folded along their width at a certain angle. A small mirror (\(2 \times 2\ \mathrm{mm}^2\)) was pressed against the adjoining edges by means of a strong spring placed between the plates; the opposite ends of the plates were fixed in the sockets of massive bases. The lateral surfaces of the plates were furnished with tinfoil electrodes, to which the variable voltage was applied. The elongation of the plates at an operating voltage of about \(5\ \mathrm{kV}\) reached \(1\ \mu\) and was determined from the displacement of the light spot reflected by the mirror. Damping of the system was achieved by immersing it in oil. A special device protected the plates from bending.

At a low frequency the deflection of the spot is proportional to the applied voltage. At constant voltage the deflection remains constant in the frequency interval from 5 to 1200 hertz, and then increases somewhat. (20—

The natural frequency of the oscillograph is about 20 kilocycles. The sensitivity of the oscillograph is 135 V/mm, and the power consumption is 0.4 VA. Investigation of the frequency characteristic showed the applicability of the oscillograph for recording processes having frequencies up to 8 kilocycles; this, together with the negligible power consumption, is the greatest valuable quality of the piezoelectric oscillograph, which is also distinguished by its small dimensions.
(W. Philippoff, ETZ. 53, 405, 1932).