US 4,122,713 A · Liquid velocity measuring system

Abstract

A liquid velocity measuring system is described utilizing ultrasonic waves to measure the velocity of a liquid and in particular, the velocity of blood as directed through a conduit external of the patient's body. The liquid velocity measuring system comprises an ultrasonic soundwave transmitting transducer energized by a continuous wave generator, preferably at a frequency of 3.13 MHz. The transmitting transducer is disposed with respect to the conduit such that the transmitted ultrasonic waves are backscattered or reflected from ultrasonic reflection centers in the blood. This signal is received and detected by a second ultrasonic transducer. The reflected ultrasonic wave is frequency-shifted dependent upon the velocity of the liquid directed through the conduit and is detected by the second transducer to be amplified and demodulated subsequently, before being applied to a microbubble detection circuit in accordance with the teachings of this invention. In particular, the microbubble detection circuit rectifies and filters the backscattered signal before applying it to a comparator circuit. In the presence of microbubbles within the liquid, the reflected ultrasonic wave will increase in amplitude at least 15-fold over that liquid, and in particular, blood without microbubbles. The comparator is set to provide an output signal if the strength of the detected signal increases 15-fold, to provide an output signal for setting a flip-flop whose output in turn energizes an alarm indicative of the presence of microbubbles.

Claims12

Dependent claims

An ultrasonic wave system for measuring the characteristics of a liquid flowing through a conduit, said system comprising:

(a) first and second transducer elements operatively associated with the conduit for respectively transmitting an ultrasonic wave into the liquid flowing through the conduit and for receiving an ultrasonic wave backscattered by the liquid directed through the conduit;
(b) generator means for applying a high-frequency signal to said first transducer element causing it to emit the ultrasonic wave into the liquid;
(c) said second transducer element providing an electrical output signal of a frequency corresponding to that high frequency of said generator means, amplitude-modulated in accordance with the backscattered signal derived from the liquid, the frequency having been shifted from that high frequency of said generator means by the Doppler phenomenon, dependent upon the velocity of the liquid directed through the conduit and whose amplitude is dependent on the acoustic impedance of the liquid;
(d) first means coupled to receive the electrical output of said second transducer element for providing an amplitude demodulated output signal, bearing frequency components of the shifted frequency;
(e) second means responsive to an increase in the amplitude output of said demodulating means for providing an alarm manifestation indicating an increase in the acoustic impedance due to presence of gaseous bubbles within the liquid directed through the conduit;
and
(f) third means coupled to receive the output signal of said first means and responsive to the frequency shift for providing a manifestation of the rate of the liquid flow.

4 more elements

An ultrasonic wave system for measuring the characteristics of a liquid flowing through a conduit, said system comprising:

(a) first and second transducer elements operatively associated with the conduit for respectively transmitting an ultrasonic wave into the liquid flowing through the conduit and for receiving an ultrasonic wave backscattered by the liquid directed through the conduit;
(b) generator means for applying a high-frequency signal to said first transducer element causing it to emit the ultrasonic wave into the liquid;
(c) said second transducer element providing an electrical output signal of a frequency corresponding to that high frequency of said generator means, amplitude-modulated in accordance with the backscattered signal derived from the liquid, the frequency having been shifted from that high frequency of said generator means by the Doppler phenomenon, dependent upon the velocity of the liquid directed through the conduit and whose amplitude is dependent on the acoustic impedance of the liquid;
(d) first means coupled to receive the electrical output of said second transducer element for amplitude demodulating its output;
and
(e) second means comprising a comparator for making comparison between the amplitude of the output of said first means and a reference signal for providing an alarm manifestation indicating an increase in the acoustic impedance due to presence of gaseous bubbles within the liquid directed through the conduit, and memory means coupled to the output of said comparator for providing a first output signal upon being actuated by the output of said comparator, a first alarm responsive to the first output signal to provide a visual manifestation of the presence of the gaseous bubbles within the liquid directed through the conduit, and a second alarm coupled to a second output of said memory means for providing an indication of the absence of gas bubbles within the liquid.

3 more elements

Dependencies are inferred from the claim text.

Liquid velocity measuring system

Life of this patent

Liquid velocity measuring system

Life of this patent

Abstract

Claims12