DEVICE FOR FORMING OF PULSES OF RESPIRATORY MOVEMENTS

The invention relates to a circuit arrangement for generation of pulses for the measurement of the tidal volume which reliably ensures, after further processing, digital display of the tidal volume under the practical conditions of anaesthetic and therapeutic ventilation, for example different compositions of the anaesthetic gas, variations in respiratory pressure and temperature as well as any expiratory moisture. It is the object of the invention to provide a circuit arrangement for generation of pulses which has to control the emitting frequency in such a way that the change in the sound propagation velocity during a change of the gas parameters is compensated and forms a wave which is stationary relative to the mechanical oscillator displacement. This object is achieved in that an ultrasonic receiver is connected to an amplifier which is connected, on the one hand, to a demodulator and its pulse output and, on the other hand, via a trigger to an input of a phase comparator circuit and a coincidence circuit whose other input and the second input of the phase comparator circuit are linked to an ultrasonic emitter, and in that the output of the phase comparator circuit is connected via a filter to an input of a summer whose other input is signal-linked to a voltage source and whose output is signal-linked via a voltage-controlled oscillator to the ultrasonic emitter.