Abstract: A piezoelectric detector for determination of the mass or film thickness of gaseous, liquid or solid substances being adsorbed or condensed on the surface of a piezoelectric resonator, having at least one measuring resonator with at least one integrated thin-film sensor, one discrete or integrated on the resonator re-evaporation heating element, and a reference resonator separated from the measuring resonator with a contamination shield, and protected from contamination, but not from heat radiation, with an optical window, which all allow correction by electronic or numerical means of influences of temperature changes on the resonant frequency and of cut-angle deviations and the temperature differences between the resonators.

Abstract: A signal generator includes a high frequency oscillator such as a quartz crystal oscillator at a frequency of 4.19 MHz, a low frequency quartz oscillator with a frequency of 32 kHz, a beat frequency generator for producing a correction signal which is transmitted to a programmable frequency divider, and an electronic switch for periodic switching of the high frequency quartz oscillator. By periodically switching-on the high frequency quartz oscillator, comparing its frequency curve with that of the low frequency quartz oscillator and and appropriately adjusting the programmable frequency divider, the advantages of long term stability, temperature of behavior and aging of a high frequency oscillator are combined with the low current consumption characteristics associated with the low frequency quartz oscillator, whereby the life of a battery powering the signal generator can be substantially extended.

Abstract: A yzw 35.degree.0' thickness shear crystal bar is provided with bevels cut n its longest narrow surfaces (b, c) proximate the ends in order to obtain energy trapping of the coupled mode vibrations which may arrive at said ends and thus permit shortening of the bar for a given quality factor.

Abstract: A multiple resonator or filter is described in the form of a rectangular of piezoelectric material having dimensional ratios selected so as to assure vibration in a thickness shear mode strongly coupled with a flexural mode. At least two energy trapping zones are provided extending over the entire width of the bar. The arrangement enables achievement of a high quality factor combined with extremely small dimensions.