GB855570A - Improvements in pressure indicating devices - Google Patents

Abstract

855,570. Electric measuring systems. KUHN, L. March 13, 1958 [May 13, 1957], No. 8113/58. Class 40 (1). [Also in Group XL (c)] Apparatus for calibrating a transducer measuring the pressure in an I.C. engine cylinder comprises piezo-crystal for measuring the pressure directly and a diaphragm subjected to the cylinder pressure and a known pressure to give an indication when the two are equal. The transducer 8 (Fig. 1), is mounted in the cylinder head 9 and comprises a piezo-crystal 1 subjected via a member 2 to the internal pressure p, and a metal diaphragm 3 subjected on the one face to the internal pressure p and on the other face to the calibrating pressure p1, so that when p#p1 the diaphragm 3 contacts a member 4 to produce a rectangular signal starting and finishing when p=p1 in each cycle. These rectangular signals, produced at 12 in Fig. 2, are amplified at 15 and differentiated separately at 16, 17 to give a short pulse at their start and finish. The pulses from 17 are superposed at 20 on a time base, voltage from generator 21 to give the waveform shown in Fig. 3, 3E, and fed to the horizontal plates 13h of a cathode-ray oscilloscope 13. The pulses from 16 are given a small time delay at 18 and superposed at 19 on the measuring signal from the piezo-crystal, developed at 11 and amplified at 14, to give the waveform shown in Fig. 3D, and fed to the vertical plates 13v of the cathode-ray oscilloscope 13. The cathode-ray oscilloscope thus produces the cyclic waveform 3F of Fig. 3. The pulses are emphasized on the cathode-ray oscilloscope screen by feeding on to the control grid rectangular pulses derived from a monostable circuit 22, controlled by the short pulses from differentiator 16.