Abstract: Selfadjusting capacitive level switch for a non-contact or contact sensing of media or objects comprising a sensor (S6), on a dielectric body (db) of which between an opposite plate (op) and a plate (p) a screening plate (sp) is mounted. Starting from the plate (p) there are alternately mounted additional screening plates (sp.sub.1, . . . , sp.sub.n+1) connected through a resistor (r1) to the screening plate (sp) and additional plates (p.sub.1, . . . , p.sub.n). Groups of additional plates (p.sub.1, . . . , p.sub.n+1) are connected through resistors to the inverting input of an operational amplifier (1). At the beginning of each oscillation halfperiod the potential of the plates (p, p.sub.1, . . . , p.sub.n) has a phase opposite to the phase of the screening plates (sp, sp.sub.1, . . . , sp.sub.n+1). The level switch detects electrically very poorly conductive materials with the relative permittivity near to 1 even through a thick, electrically well conductive deposit on its sensor.

Abstract: A level switch includes an operational amplifier, provided with positive and negative feedback, and a sensor, together forming an astable multivibrator. The oscillation onset and frequency of the multivibrator depend on the surface level of controlled material. The sensor includes a dielectric body on which, starting from its fastening end, a grounded opposite electrode and a screening electrode, connected to the amplifier output, are mounted. A ring plate connected to the inverting amplifier input is incorporated coaxially in the dielectric body. The level switch need not be adjusted when the controlled material is changed, although materials may have quite different electrical properties and may stick to the sensor.

Abstract: The converter input i is connected through a comparator to the polarity bit output as well as to the input of a full-wave precision rectifier in the first quantization stage, which like further stages comprises an operational amplifier, a comparator and an exclusive OR gate, the output of which is connected to the output for the first bit. To the inverting input of the amplifier with the gain equal to 2 through the potentiometer a voltage -U.sub.o /2 is fed, (-U.sub.o, +U.sub.o) being the interval of the input voltage. The input of the rectifier is connector to the input i and the input of the rectifier in further stages is connected to the output of the operational amplifier in the previous stage. The second input of the exclusive OR gate is connected to the bit output of the previous stage.