SENSOR

Abstract

A sensor having a chamber with a sensor element arranged therein comprises a first volume of air. The sensor has a tubular air supply to the chamber, the air supply comprising a second volume of air, and penetration of water through the air supply to the sensor element being prevented by the dimensions of the air supply that define the second volume.

Claims

1. A sensor, having a chamber with a sensor element arranged therein, the chamber comprising a first volume (V.sub.1) of air, and having a tubular air supply to the chamber, the air supply comprising a second volume (V.sub.2) of air, penetration of water through the air supply to the sensor element being prevented by the dimensions of the air supply that define the second volume (V.sub.2).

2. The sensor according to claim 1, in which water is prevented from getting into the chamber by the dimensions of the air supply.

3. The sensor according to claim 1, in which the maximum inside diameter of the air supply is significantly less than the extent of the chamber (3) perpendicular to the inflow direction of the air.

4. The sensor according to claim 1, in which the second volume (V.sub.2) is at least as large as the first volume (V.sub.1).

5. The sensor according to claim 1, in which penetration of water to the sensor element is prevented at least to a prescribed maximum water depth d.sub.max in meters, the following condition applying for the ratio of the second volume (V.sub.2) to the first volume (V.sub.1): V.sub.2/V.sub.1>0.1 m.sup.−1.Math.d.sub.max.

6. The sensor according to claim 1, in which penetration of water to the sensor element is prevented at least to a water depth of 20 m.

7. The sensor according to claim 1, which does not have a barrier element to protect against penetration of water to the sensor element.

8. The sensor according to claim 9, which does not have a barrier element formed as a membrane.

9. The sensor according to either of claims 7, which does not have a barrier element formed as a gel.

10. The sensor according to claim 1, in which the air supply is formed from a flexible material.

11. The sensor according to claim 1, in which the air supply is integrated in a housing.

12. The sensor according to claim 11, in which the housing is injection-molded, the air supply being formed during the injection molding.

13. The sensor according to claim 1, in which the air supply has at least one kink or bend.

14. The sensor according to claim 1, in which the sensor element is surrounded laterally and upwardly by the first volume (V.sub.1).

15. The sensor according to claim 1, which is suitable for use in a cell phone, a wristwatch or an armband.

16. The sensor according to claim 1, which is designed as a pressure sensor, as an air humidity sensor or as a gas sensor.

17. The sensor according to claim 1, wherein the length of the air supply is significantly greater than an inside diameter of the air supply.

18. The sensor according to claim 1, wherein a maximum inside diameter of the air supply is so small that, when immersed in water, enclosed air cannot escape to the outside through the air supply.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG. 1 shows a sensor according to one embodiment in a schematic sectional view.

DETAILED DESCRIPTION OF ONE OR MORE EMBODIMENTS

[0026] FIG. 1 shows a sensor 1, which is for example designed as a pressure sensor. The sensor 1 has a sensor element 2, which is arranged in a chamber 3. Within the chamber 3 there is a first volume V.sub.1 of air, which partially surrounds the sensor element 2. In particular, the sensor element 2 is surrounded laterally and upwardly by the first volume V.sub.1. The first volume V.sub.1 is connected to an outside space 5 by a tubular air supply 4. The sensor 1 has an open structure, so that air and water can get into the air supply 4 from the outside.

[0027] The chamber 3 is partially delimited by a housing 6. The housing 6 has an opening 7, from which the air supply 4 leads away. In the embodiment shown, the air supply 4 is partially inserted in the opening 7. The air supply 4 may for example also be completely inserted in the opening 7 or outwardly adjoin the opening 7. The chamber 3 is laterally delimited by a sealing element 8, which is for example designed as a sealing ring. The sealing element 8 seals off the chamber 3 in an airtight manner. The sensor element 2 is arranged on a carrier 9, in particular a printed circuit board. The carrier 9 delimits the chamber 3 in the downward direction.

[0028] The housing 6 may enclose still further components of the sensor 1. For example, further components, in particular electronic components, are arranged in a further inside space 10, which is sealed off in an airtight manner from the chamber 3 by the sealing element 8. In particular, the air-filled volume V.sub.1 is separated in an airtight manner from the further inside space 10. In this case, the sealing element 5 is airtight at least in the working pressure range, in particular under an outside pressure in a range between atmospheric air pressure and a prescribed maximum pressure. Consequently, an air flow from the volume V.sub.1 is only possible into the air supply 4, but not into other regions of the sensor 1. The further inside space 10 is preferably closed off from the outside space 5 in an airtight and waterproof manner. Consequently, the air pressure in the further inside space 10 is preferably constant, for example always at normal pressure.

[0029] The first volume V.sub.1 is connected to the outside space 5 by way of the second volume V.sub.2 in an air-permeable manner. The air supply 4 is in this case designed such that, when the sensor 1 is immersed in water, the water can get into the air supply 4 by way of an outer opening 11. Since, apart from the outer opening 11, the air supply 4 is only connected in an air-permeable manner to the chamber 3 and, apart from the air supply 4, the chamber 3 is closed off in an airtight manner, the air enclosed in the air supply 4 and the chamber 3 cannot escape. Consequently, the air located within the air supply 4 and the chamber 3 is compressed until the pressure of the air corresponds to the outside pressure. The air supply 4 has such dimensions that, under an outside pressure that is less than or equal to a prescribed maximum pressure, the water getting in cannot enter the chamber 3.

[0030] The depicted sensor 1 is for example waterproof at least to a depth d.sub.max=20 m. According to the condition V.sub.2/V.sub.1>=0.1 m.sup.−1.Math.d.sub.max, the second volume is at least twice the first volume. Often, waterproofness to a depth of 50 m is desired. In this case, the second volume is at least five times the first volume.

[0031] For example, the sensor element 2 has dimensions of 2 mm×2 mm×0.8 mm (width×length×height). The chamber 3 is for example outwardly bounded by a sealing element 8 in the form of a sealing ring and has for example a lateral diameter of 2.5 mm and a height of 1 mm. The first volume V.sub.1 within the chamber 3 is calculated from the difference between the chamber volume and the volume taken up by the sensor element as 1.7 mm.sup.3. With a prescribed maximum water depth of 20 m, a second volume V.sub.2 of at least 3.4 mm.sup.3 is obtained. Consequently, with an inside diameter of the air supply 4 of 0.8 mm, the air supply 4 should have a length of at least 6.8 mm.

[0032] The air supply 4 has a bent shape. The air supply 4 is preferably arranged within an outer housing (not depicted) of the sensor 1. In particular, the air supply 4 does not protrude out of the outer housing. The outer housing may also be formed as one part with the housing 6. For example, the housing reaches as far as the opening of the air supply 4 to the outside space 5. The outer housing may however also be formed as a separate component from the housing 6.

[0033] In one embodiment, the air supply 4 is designed as a separate element. For example, the air supply 4 is formed by a flexible material. For example, the material comprises silicone. In an alternative embodiment, the air supply 4 is integrated in an outer housing. For example, the outer housing is injection-molded. The air supply 4 may be formed in the injection-molding process as a passage through the housing.