Air bubble detector
View Patent ↗Air bubbles may be characterized by an air bubble detector by choosing an optimum set of frequencies and then comparing a return signal from a sensor receiving those frequencies against an internal reference. The number of pulses that exceed the internal reference represents a width and may be counted. The width, as counted, may be correlated to bubble characteristics including volume.
1. A method of detecting bubbles comprising:
sending a first ultrasonic signal through a fluid path by an ultrasonic transmitter, the signal corresponding to a first range of ultrasonic frequencies;
reporting a detected signal by an ultrasonic receiver;
selecting an internal receiver signal reference;
determining the amount of time the detected signal exceeds the internal reference; and
calculating bubble size based on the amount of time the detected signal exceeds the internal reference;
determining a resonant frequency based upon the detected signal from the first range of ultrasonic frequencies;
storing the resonant frequency;
sending a second ultrasonic signal through the fluid path by the ultrasonic transmitter, the signal corresponding to a second range of ultrasonic frequencies surrounding the resonant frequency;
resending the first ultrasonic signal after a degradation in the detected signal is detected from sending the second ultrasonic signal; and
redetermining the resonant frequency based upon the detected signal from the resending of the first range of ultrasonic frequencies.
2. The method of claim 1 , further comprising resending the first ultrasonic signal after a predetermined time period from sending the first ultrasonic signal; and
redetermining the resonant frequency based upon the detected signal from the resending of the first range of ultrasonic frequencies.
3. The method of claim 1 , further comprising resending the first ultrasonic signal after an environmental change is detected; and
redetermining the resonant frequency based upon the detected signal from the resending of the first range of ultrasonic frequencies.
4. The method of claim 1 , wherein sending the second ultrasonic signal uses less power than sending the first ultrasonic signal.