# US 11,112,384 B2 · Methane gas sensor

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- Number: US 11,112,384 B2
- Document ID: US11112384B2
- Status: Granted
- Kind: B2
- Application number: 16/810,325
- Filed: 2020-03-05
- Published: 2020-08-06
- Granted: 2021-09-07
- Earliest claimed: 2018-02-17
- Assignees: Applied Nanotech, Inc.
- Applicants: Applied Nanotech, Inc.
- Inventors: Igor Pavlovsky
- Web page: https://patentgrep.com/patent/US11112384B2

## CPC

- G01N 29/022: {Fluid sensors based on microsensors, e.g. quartz crystal-microbalance [QCM], surface acoustic wave [SAW] devices, tuning forks, cantilevers, flexural plate wave [FPW] devices (microdevices per se B81B)}
- G01N 29/036: by measuring frequency or resonance of acoustic waves
- G01N 29/326: {compensating for temperature variations}
- G01N 33/0047: {Organic compounds}
- G01N 33/0063: {using a threshold to release an alarm or displaying means}
- G08B 21/16: Combustible gas alarms
- H05K 1/18: structurally associated with non-printed electric components (H05K1/16 takes precedence)
- H05K 5/069: {Other details of the casing, e.g. wall structure, passage for a connector, a cable, a shaft}
- H05K 5/13: assembled by screws
- H05K 7/20: Modifications to facilitate cooling, ventilating, or heating
- G01N 2291/0215: Mixtures of three or more gases, e.g. air
- G08B 29/24: Self-calibration, e.g. compensating for environmental drift or ageing of components
- H05K 2201/10022: Non-printed resistor
- H05K 2201/10083: Electromechanical or electro-acoustic component, e.g. microphone
- H05K 2201/10151: Sensor
- 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)
- G08B: SIGNALLING SYSTEMS, e.g. PERSONAL CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS

## Abstract

An apparatus and method for detection of methane in an environment, including a housing with a sensor printed circuit board and a processor printed circuit board interconnected to and thermally insulated from the sensor printed circuit board. The sensor printed circuit board includes a first tuning fork isolated from the environment, and a second tuning fork exposed to the environment. The tuning forks are attached to opposite sides of the sensor printed circuit board. The processor printed circuit board includes processing circuitry interconnected to the first tuning fork and the second tuning fork, which receives vibration frequency signals therefrom, and is programmed to determine a frequency difference between the frequency of vibration of the first tuning fork and the frequency vibration of the second tuning fork, and if the frequency difference is greater than a predetermined threshold, then setting an alarm to indicate the presence of methane.

## Claims

### Claim 1

An apparatus for detection of methane in an environment, the apparatus comprising
a housing comprising a sensor printed circuit board and a processor printed circuit board interconnected to the sensor printed circuit board,
the sensor printed circuit board comprising
a first tuning fork, and
a second tuning fork, the second tuning fork being exposed to the environment,
wherein the first tuning fork and the second tuning fork are attached to opposite sides of the sensor printed circuit board;
the processor printed circuit board comprising
processing circuitry interconnected to the first tuning fork and the second tuning fork and programmed to
determine a frequency difference between the frequency of vibration of the first tuning fork and the frequency of vibration of the second tuning fork, and
if the frequency difference is greater than a predetermined threshold, then setting an alarm to indicate the presence of methane.

### Claim 2 (depends on 1)

The apparatus of claim 1 wherein
the processing circuitry comprises a D flip-flop and a microcontroller, wherein
the vibration frequency signals from the tuning forks are interconnected to the D input and clock input of the D flip-flop for determining the differential frequency,
the trigger output of the D flip-flop is interconnected to the microcontroller that counts pulses within a certain time period by modulating an external high frequency carrier signal;
wherein the number of pulses counted is a nearly linear function of the methane concentration.

### Claim 3 (depends on 1)

The apparatus of claim 1 wherein the first tuning fork and the second tuning fork each comprise a quartz oscillator.

### Claim 4 (depends on 1)

The apparatus of claim 1 further comprising a casing in which the first tuning fork is located, the casing being vacuum sealed to provide temperature and pressure isolation from the environment.

### Claim 5 (depends on 4)

The apparatus of claim 4 further comprising a heating element mounted in proximity to the casing wherein the casing is heated by the heating element.

### Claim 6 (depends on 1)

The apparatus of claim 1 further comprising a pressure sensor, a humidity sensor, and a thermistor each mounted within the housing and interconnected with the processing circuitry on the processor printed circuit board.

### Claim 7

A method for detection of methane in an environment, the method comprising
providing in a housing
a sensor printed circuit board, and
a processor printed circuit board interconnected to the sensor printed circuit board,
providing on the sensor printed circuit board
a first tuning fork, and
a second tuning fork, the second tuning fork being exposed to the environment,
wherein the first tuning fork and the second tuning fork are attached to opposite sides of the sensor printed circuit board;
providing on the processor printed circuit board
processing circuitry interconnected to the first tuning fork and the second tuning fork
wherein the processing circuitry
determines a frequency difference between the frequency of vibration of the first tuning fork and the frequency of vibration of the second tuning fork, and
sets an alarm to indicate the presence of methane if the frequency difference is greater than a predetermined threshold.

### Claim 8 (depends on 7)

The method of claim 7 wherein
the processing circuitry comprises a D flip-flop and a microcontroller,
the vibration frequency signals from the tuning forks are interconnected to the D input and clock input of the D flip-flop for determining the differential frequency,
the trigger output of the D flip-flop is interconnected to the microcontroller that counts pulses within a certain time period by modulating an external high frequency carrier signal; and
the number of pulses counted is a nearly linear function of the methane concentration.

### Claim 9 (depends on 7)

The method of claim 7 wherein the first tuning fork and the second tuning fork each comprise a quartz oscillator.

### Claim 10 (depends on 7)

The method of claim 7 further comprising providing a casing in which the first tuning fork is located, the casing being vacuum sealed to provide temperature and pressure isolation from the environment.

### Claim 11 (depends on 10)

The method of claim 10 further comprising mounting a heating element in proximity to the casing wherein the casing is heated by the heating element.

### Claim 12 (depends on 7)

The method of claim 7 further comprising mounting a pressure sensor, a humidity sensor, and a thermistor within the housing and interconnecting them with the processing circuitry on the processor printed circuit board.