Abstract: Circuitry and a sensor suitable for measuring blood pressure is described. The sensor of the present invention has a flexible piezoelectric material covering the opening of a chamber. The chamber contains an electrically nonconductive, elastomeric material, and needs no pump to pressurize the chamber. An array of sensors and circuitry for measurement of fluid pressure fluctuation in a flexible environment is given.

Abstract: A multi-function circuit including an oscillator, a pulse generator and an integrator which share a common timing capacitor. The pulse generator is run by double ended charging of the timing capacitor. The integrator shares the threshold setting circuitry of the oscillator and in turn the pulse generator shares and makes use of the threshold setting circuitry of both the integrator and the oscillator. During operation of the pulse generator, positive feedback through the capacitor aids in providing a rapid and complete discharging of the timing capacitor 16 below the lower threshold of the oscillator. A selector input selects between the oscillator and pulse generator and the integrator provides a predetermined time delay in which the selection is verified.

Abstract: An oscillator circuit is disclosed in which a charging path is provided through a charging transistor and a discharging path is provided through a discharging transistor. Both the charging path and discharging path are directed through a first and second terminal for connection across a timing resistor to allow for reliable 50% duty cycle operation. A diode is provided between a voltage limit setting circuit and a second diode. The second diode is connected to the base of a buffer transistor. The buffer transistor turns the discharging transistor on and off. The two diodes provide a delay between the time in which the voltage limit setting circuitry changes the voltage limit and the switching of the discharging transistor to prevent latch-up.