Air bubble detector

• US 8,539,812 B2
• Filed: 02/05/2010
• Issued: 09/24/2013
• Est. Priority Date: 02/06/2009
• Status: Active Grant

• Current Assignee: Zevex (Moog Incorporated)
• Original Assignee: Zevek Incorporated
• Inventors: Stringham, Mark, Millis, Roger, Foley, John, Blaine, David
• Primary Examiner(s): Macchiarolo, Peter
• Assistant Examiner(s): BELLAMY, TAMIKO D
• Application Number:
  US12/701,506
• Publication Number:
  US 20100212407A1
• Time in Patent Office: 1,327 Days
• Field of Search: 73/18.3, 73/18.2, 73/617.5
• US Class Current: 73/1.82
• CPC Class Codes: G01N 2291/02433 Gases in liquids, e.g. bubbles, foams
• CPC Class Codes: G01N 2291/048 Transmission, i.e. analysed material between transmitter and receiver
• CPC Class Codes: G01N 2291/102 one emitter, one receiver
• CPC Class Codes: G01N 29/032 by measuring attenuation of acoustic waves
• CPC Class Codes: G01N 29/036 by measuring frequency or resonance of acoustic waves
• CPC Class Codes: G01N 29/348 with frequency characteristics, e.g. single frequency signals, chirp signals measuring frequency of mechanical vibrations or acoustic waves in general G01H1/06, G01H3/04; measuring frequency or analysing frequency spectra G01R23/00

Abstract

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.

Claims

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.