Photoacoustic gas sensor device

1. A photoacoustic gas sensor device, for determining a value indicative of a presence or a concentration of a component in a gas, the photoacoustic gas sensor device comprising:

a substrate,

a measurement cell body arranged on a first side of the substrate,

the substrate and the measurement cell body defining a measurement cell enclosing a measurement volume,

the measurement cell comprising an aperture for a gas to enter the measurement volume,

an electromagnetic radiation source for emitting electromagnetic radiation,

a microphone for measuring a sound wave generated by the component in response to an absorption of electromagnetic radiation by the component,

wherein the electromagnetic radiation source and the microphone are arranged on the first side of the substrate and in the measurement volume,

wherein the microphone has a bottom port facing the substrate, and

wherein the measurement volume is communicatively coupled to the bottom port.

2. The photoacoustic gas sensor device according to claim 1 ,

wherein dimensions of the measurement cell are smaller than 2×2×2 cm 3 .

3. The photoacoustic gas sensor device according to claim 1 ,

wherein an inner surface of the measurement cell has a reflectivity of more than 70%.

4. The photoacoustic gas sensor device according to claim 1 ,

wherein an inner surface of the measurement cell body and/or a part of the substrate is coated with a reflective coating having a reflectivity of more than 70%.

5. The photoacoustic gas sensor device according to claim 1 ,

wherein a ratio of inner surfaces of the measurement cell with a reflectivity of above 70% to inner surfaces of the measurement cell with a reflectivity of below 70% is above 20.

6. The photoacoustic gas sensor device according to claim 4 ,

wherein a top side of the microphone facing the measurement volume is made of a reflective material or is coated with the reflective coating.

7. The photoacoustic gas sensor device according to claim 1 ,

wherein an opening between the measurement volume and the bottom port of the microphone has a dimension perpendicular to the first side of the substrate of more than 10 μm.

8. The photoacoustic gas sensor device according to claim 1 ,

wherein an opening between the measurement volume and the bottom port of the microphone is laterally defined by a solder or a spacer between the microphone and the substrate.

9. The photoacoustic gas sensor device according to claim 1 , further comprising

a controller configured to control the electromagnetic radiation source,

wherein the controller is configured to control an intensity of the electromagnetic radiation to modulate with a modulation frequency,

wherein the modulation frequency is between 1 Hz and 100 kHz.

10. The photoacoustic gas sensor device according to claim 9 ,

wherein the controller is configured to receive a measurement signal from the microphone and to determine the value indicative of a presence or a concentration of the component dependent on the measurement signal.

11. The photoacoustic gas sensor device according to claim 1 , further comprising

a gas permeable membrane covering the aperture,

wherein the membrane is permeable for a gas exchange between the measurement volume and surroundings of the measurement cell,

wherein the gas permeable membrane is made of one or more of the following materials: sintered metal, ceramic, plastic.

12. The photoacoustic gas sensor device according to claim 9 ,

wherein the electromagnetic radiation source is an infrared source, wherein the infrared source is one of the following:

a broadband source covered by a wavelength-selective bandpass filter filtering out infrared radiation outside the band,

a narrowband source comprising a meta-surface resonator, and

wherein a heater of the infrared source is switched with the modulation frequency.

13. The photoacoustic gas sensor device according to claim 1 , further comprising

a second sensor for sensing one or more of temperature, humidity, pressure, one or more different components in a gas, arranged on or integrated in the substrate, and

located inside the measurement cell.

14. The photoacoustic gas sensor device according to claim 9 ,

further comprising a second sensor for sensing one or more of temperature, humidity, pressure, one or more different components in a gas, arranged on or integrated in the substrate,

wherein the controller is configured to compensate the value indicative of a presence or a concentration of the component dependent on measurement values of the second sensor.

15. The photoacoustic gas sensor device according to claim 1 ,

wherein the electromagnetic radiation source and the microphone are arranged on the first side of the substrate by surface mounting.

16. The photoacoustic gas sensor device according to claim 1 for use as a CO2 sensor,

wherein the electromagnetic radiation source is an infrared source,

wherein the band of infrared radiation is centered around a wavelength of 4.3 μm.

17. The photoacoustic gas sensor device according to claim 4 ,

wherein the reflective coating is made from a metal.

18. The photoacoustic gas sensor device according to claim 10 ,

wherein the controller is configured to determine the value indicative of a presence or a concentration of the component dependent on an amplitude of the measurement signal.

19. The photoacoustic gas sensor according to claim 15 ,

wherein all electronic components are arranged on the first side of the substrate by surface mounting while a second side of the substrate opposite the first side only includes contacts for electrically connecting to the photoacoustic gas sensor device.

20. The photoacoustic gas sensor device according to claim 16 ,

wherein the band has a full width at half maximum of below 0.5 μm.