# US 8,539,812 B2 · Air bubble detector

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- Number: US 8,539,812 B2
- Document ID: US8539812B2
- Status: Granted
- Kind: B2
- Application number: 12/701,506
- Filed: 2010-02-05
- Published: 2010-08-26
- Granted: 2013-09-24
- Earliest claimed: 2009-02-06
- Assignees: Zevek, Inc.
- Applicants: Mark Stringham; Roger Millis; John Foley; David Blaine
- Inventors: Mark Stringham; Roger Millis; John Foley; David Blaine
- Web page: https://patentgrep.com/patent/US8539812B2

## CPC

- G01N 29/036: by measuring frequency or resonance of acoustic waves
- G01N 29/032: by measuring attenuation of acoustic waves
- 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)}
- G01N 2291/02433: Gases in liquids, e.g. bubbles, foams
- G01N 2291/048: Transmission, i.e. analysed material between transmitter and receiver
- G01N 2291/102: one emitter, one receiver
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## 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

### Claim 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.

### Claim 2 (depends on 1)

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.

### Claim 3 (depends on 1)

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.

### Claim 4 (depends on 1)

The method of claim 1, wherein sending the second ultrasonic signal uses less power than sending the first ultrasonic signal.