# US 8,739,601 B2 · Air bubble detector

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- Number: US 8,739,601 B2
- Document ID: US8739601B2
- Status: Granted
- Kind: B2
- Application number: 13/594,142
- Filed: 2012-08-24
- Published: 2012-12-13
- Granted: 2014-06-03
- Earliest claimed: 2009-02-06
- Assignees: Zevex, 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/US8739601B2

## 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 bubble detection system comprising:
a fluid path;
a piezoelectric transmitter and a piezoelectric receiver disposed adjacent the fluid path for detecting bubbles therein; and
control circuitry for operating the transmitter and receiver comprising:
a circuit for generating a wide range frequency sweep in the transmitter;
a circuit for analyzing the receiver output and determining a resonant frequency for the piezoelectric transmitter and receiver and fluid path;
memory for storing the resonant frequency;
a circuit for operating the transmitter at a reduced frequency range at the resonant frequency in order to thereby detect bubbles in the fluid path:
a comparator circuit for comparing the receiver signal while detecting bubbles to a signal threshold to determine if bubbles are present;
wherein the comparator circuit determines the time period for which a signal exceeds the signal threshold and determines bubble size based on the time period.

### Claim 2 (depends on 1)

The system of claim 1, wherein the circuit for generating a wide range frequency sweep in the transmitter comprises a voltage ramp generating circuit and a voltage driven frequency generation circuit.

### Claim 3 (depends on 1)

The system of claim 1, wherein the fluid path comprises a tube for delivering a liquid.

### Claim 4 (depends on 1)

The system of claim 1, wherein the circuit for analyzing the receiver out and determining a resonant frequency for the piezoelectric transmitter and receiver and fluid path comprises a comparator circuit.

### Claim 5 (depends on 1)

The system of claim 1, further comprising a medical pump configured to pump fluid through the fluid path.

### Claim 6 (depends on 5)

The system of claim 5, wherein the control circuitry is configured to control the transmitter to send the wide range frequency or the reduced frequency range at a time that is based upon a flow rate of the fluid through the fluid path.

### Claim 7 (depends on 1)

The system of claim of claim 1, wherein the piezoelectric transmitter and piezoelectric receiver includes a plurality of piezoelectric transmitters and a plurality of piezoelectric receivers spaced along the fluid path.

### Claim 8 (depends on 7)

The system of claim 7, wherein the plurality of piezoelectric transmitters and the plurality of piezoelectric receivers are spaced at regular intervals along the fluid path.