Abstract: Systems and methods are provided for sensing or measuring capacitive or inductive reactance or changes in reactance in which the sensed reactance is coupled with a known resistance in a sensor circuit and a start signal is provided to the sensor circuit, and a programmable delay line is used to generate a programmable delay signal. The outputs of the programmable delay and the sensor circuits are compared to ascertain which transitions first, and the programmable delay value is adjusted in successive approximation fashion to identify a programmable delay that best represents the delay time of the sensor circuit from which the sensed reactance value can be determined.

Abstract: Systems and methods are provided for sensing or measuring capacitive or inductive reactance or changes in reactance in which the sensed reactance is coupled with a known resistance in a sensor circuit and a start signal is provided to the sensor circuit, and a programmable delay line is used to generate a programmable delay signal. The outputs of the programmable delay and the sensor circuits are compared to ascertain which transitions first, and the programmable delay value is adjusted in successive approximation fashion to identify a programmable delay that best represents the delay time of the sensor circuit from which the sensed reactance value can be determined.

Abstract: The detector for detecting the presence of a liquid comprises: a) a metal veguide having a solid cylindrical top first portion of relatively small section with an outside diameter having a first value d1, which first portion is fixed on a support, a cylindrical rigid bottom second portion whose outside diameter has a second value d2 greater than the first value d1, which second portion extends the first portion downwards and is connected thereto by a short linking portion; b) transducer means disposed in the vicinity of the top portion of the waveguide; and c) electronic processing means. The value of the frequency at which the transducer means are excited is selected in such a manner that acoustic wave trains propagate in the cylindrical first portion at the group velocity of low frequency waves, and propagate in the cylindrical second portion at the minimum group velocity corresponding to the point of inflection in the curve of phase velocity as a function of frequency.

Abstract: The liquid level detector using guided waves, comprises a first transducer situated out of the liquid for sending an incident elastic pulse which propagates in an elongated guide of which the lower part is immersed in the liquid, a second transducer situated out of the liquid and receiving the elastic pulse sent by the first transducer and transmitted by the guide, and electronic circuits for measuring the time elapsing between the transmission of an incident elastic pulse by the first transducer and the subsequent reception of the same elastic wave by the second transducer.

Abstract: The invention relates to data acquisition devices making it possible, by the use of elastic surface waves, to mark the coordinates of a stylus (7) making a line on the surface (2) of a piezoelectric plate (1).The invention relates to a device in which the measuring surface (2) is provided with roughnesses or unevennesses of negligible size compared with the wavelength of the surface waves. The stylus (7) also comprises a member (8) for supplying a marking substance (10).The invention is more particularly applicable to the remote transmission of graphic symbols and to the processing of digital data representing such symbols.

Abstract: An optical pickup which performs the function of a light pen is capable of point detection of elastic waves propagated by electrochemical transducers in a direction parallel to the surface of a writing table. The table is constituted by a plate of refractive material placed within an optical polarizing cell which prevents emergence of incident radiation produced by a light source. The pickup receives that portion of the radiation which emerges from the cell by virtue of the birefringence induced within the plate by the elastic wave trains issuing from the transducers.

Abstract: The invention relates to piezoelectric devices employing a piezoelectric layer deposited on a substrate devoid of piezoelectric properties at ambient temperature. The device in accordance with the invention is provided with a piezoelectric layer made from a mono-atomic crystalline material, namely selenium. The invention is applicable to the excitation of surface elastic waves along non-piezoelectric substrates, to the excitation of bulk elastic waves and to the detection of infrared radiations.