# US 2019/0170702 A1 · Photoacoustic sensor, method for checking a gas-tightness, and system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0170702 A1 - Document ID: US20190170702A1 - Status: Published application - Kind: A1 - Application number: 16/203,859 - Filed: 2018-11-29 - Published: 2019-06-06 - Earliest claimed: 2017-12-01 - Assignees: Infineon Technologies AG - Applicants: Infineon Technologies AG - Inventors: Matthias Eberl; Franz Jost; Stefan Kolb - Web page: https://patentgrep.com/patent/US20190170702A1 ## CPC - G01N 29/2431: {using other means for acoustic excitation, e.g. heat, microwaves, electron beams (sound producing devices not otherwise provided for G10K15/04)} - G01N 29/30: Arrangements for calibrating or comparing, e.g. with standard objects - G01N 21/1702: {with opto-acoustic detection, e.g. for gases or analysing solids} - G01N 29/14: using acoustic emission techniques {(echo of particles G01N29/046; measuring mechanical vibrations or acoustic waves in solids in general G01H1/00)} - G01N 29/222: {Constructional or flow details for analysing fluids (optoacoustic fluid cells G01N29/2425)} - G01N 29/2418: {using optoacoustic interaction with the material, e.g. laser radiation, photoacoustics (photoacoustic cells G01N21/1702; measuring characteristics of vibrations by using radiation-sensitive means G01H9/00; acousto-optical conversion techniques for short-range imaging G01S15/8965; sound-producing devices using laser bundle G10K15/046)} - G01N 29/2425: {optoacoustic fluid cells therefor} - G01N 29/326: {compensating for temperature variations} - G01N 2021/1704: {in gases} - G01N 2021/1708: {with piezotransducers} - 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 An example of a system comprises a volume filled with a gas, a gas excitation device configured to excite the gas inside the volume, a microphone configured to output a microphone signal on the basis of the gas excited by the gas excitation device, and a testing unit configured to take the microphone signal as a basis for testing a gas-tightness of the volume. An example of a photoacoustic sensor comprises a hermetically sealed sensor cell, a gas excitation device and a testing unit configured to take the microphone signal dependent on the thermally excited gas as a basis for testing a gas-tightness of the sensor cell. One example comprises a method for testing a gas-tightness of a volume filled with a gas. ## Claims ### Claim at position 1 1-18. (canceled) ### Claim 19 A photoacoustic sensor, comprising: a hermetically sealed sensor cell filled with a gas; a gas excitation device, inside the sensor cell, to thermally excite the gas; a microphone to output a microphone signal that is based on the thermally excited gas; and a testing unit to use the microphone signal as a basis for testing a gas-tightness of the sensor cell. ### Claim 20 A method for testing a gas-tightness of a hermetically sealed sensor cell of a photoacoustic sensor filled with a gas, comprising: exciting the gas inside the sensor cell using a gas excitation device; capturing a microphone signal on a basis of the excited gas using a microphone; and testing the gas-tightness of the sensor cell based on the microphone signal. ### Claim 21 (depends on 19) The photoacoustic sensor of claim 19, wherein the gas excitation device comprises a heating apparatus. ### Claim 22 (depends on 19) The photoacoustic sensor of claim 19, wherein the microphone signal is output on a basis of a thermoacoustic property of the thermally excited gas. ### Claim 23 (depends on 19) The photoacoustic sensor of claim 19, further comprising: a light source, located outside of the sensor cell, to photonically excite the gas to permit a concentration of the gas in the sensor cell to be determined. ### Claim 24 (depends on 23) The photoacoustic sensor of claim 23, wherein the gas excitation device comprises an electrical resistor element heatable, in order to excite the gas, based on a predetermined electrical signal. ### Claim 25 (depends on 24) The photoacoustic sensor of claim 24, wherein the electrical resistor element comprises at least a portion of a temperature sensor inside the sensor cell, wherein the temperature sensor is a PTC temperature sensor or a PT1000 temperature sensor. ### Claim 26 (depends on 19) The photoacoustic sensor of claim 19, wherein the gas excitation device comprises a photodiode to thermally excite the gas in the sensor cell based on an electrical signal applied to the photodiode. ### Claim 27 (depends on 26) The photoacoustic sensor of claim 26, wherein the electrical signal has a predetermined voltage, a predetermined frequency, and/or a predetermined duty cycle. ### Claim 28 (depends on 19) The photoacoustic sensor of claim 19, wherein the testing unit is configured to output a signal indicating that the sensor cell is gas-tight based on the microphone signal being within a particular range of a reference signal. ### Claim 29 (depends on 28) The photoacoustic sensor of claim 28, wherein the particular range is consistent with an amplitude range that comprises a difference in an amplitude of the reference signal. ### Claim 30 (depends on 29) The photoacoustic sensor of claim 29, wherein the difference comprises 10% and the particular range is consistent with an amplitude range in which amplitudes are between 90 percent and 110 percent of the amplitude of the reference signal. ### Claim 31 (depends on 19) The photoacoustic sensor of claim 19, wherein the testing unit is configured to output a signal indicating that the sensor cell is leaky based on the microphone signal being within a particular error range. ### Claim 32 (depends on 19) The photoacoustic sensor of claim 19, wherein the testing unit is configured to output a signal indicating that the sensor cell is leaky based on a change in the microphone signal over time being greater than a particular error value. ### Claim 33 (depends on 19) The photoacoustic sensor of claim 19, wherein the testing unit is configured to output a signal indicating that the microphone is defective based on the microphone signal being within a predetermined range. ### Claim 34 (depends on 19) The photoacoustic sensor of claim 19, wherein the testing unit configured to output a signal that causes the gas to be excited by the gas excitation device. ### Claim 35 A photoacoustic sensor, comprising: a hermetically sealed sensor cell filled with a gas; a gas excitation device to thermally, optically, or acoustically excite the gas; a microphone to output a microphone signal that is based on the excited gas; and a testing unit to use the microphone signal as a basis for testing a gas-tightness of the sensor cell. ### Claim 36 (depends on 35) The photoacoustic sensor of claim 35, wherein the gas excitation device is a photodiode configured to optically excite the gas. ### Claim 37 (depends on 35) The photoacoustic sensor of claim 35, wherein the testing unit is configured to output a signal indicating that the sensor cell is gas-tight based on the microphone signal being with a particular range of a reference signal. ### Claim 38 (depends on 35) The photoacoustic sensor of claim 35, wherein the testing unit is configured to output a signal indicating that the sensor cell is leaky based on the microphone signal being within a particular error range.