Vacuum measuring cell with membrane
A vacuum measuring cell with a membrane between two planar housing parts has a first housing part forming a reference vacuum volume and the second housing part forming a measuring vacuum volume with a connection for the medium to be measured and a mechanism for measuring the membrane deflection. The membrane surface exposed to the medium to be measured is a structured surface.
1. Vacuum measuring cell with a membrane ( 2 , 41 ) disposed between two planar housing parts ( 1 , 4 ), wherein the first housing part ( 1 ) forms a reference vacuum volume ( 10 ) and the second housing part ( 4 ) a measuring vacuum volume ( 9 ) with connection means ( 5 ) for the connection with the medium to be measured, and means for measuring the membrane deflection are provided, characterized in that the membrane surface ( 41 a ), which is exposed to the medium to be measured, is implemented as a structured surface, the structure of the structured surface being implemented such that an accumulation layer ( 40 ) deposited from the medium onto the membrane ( 2 , 41 ) behaves substantially stress-free with respect to the membrane, such that hereby a stress deformation of the membrane ( 2 , 41 ) is reduced.
2. Measuring cell as claimed in claim 1 , characterized in that the membrane ( 2 , 41 ) is substantially of ceramics, such as Al 2 O 3 , and/or of sapphire, such as monocrystalline Al 2 O 3 .
3. Measuring cell as claimed in claim 1 , characterized in that the vacuum measuring cell forms with the membrane ( 2 , 41 ) a capacitive and/or an optical measuring arrangement.
4. Measuring cell as claimed in claim 1 , characterized in that the thickness of the membrane is in the range of 40 μm to 760 μm and the diameter is in the range of 5 to 80 mm.
5. Measuring cell as claimed in claim 1 , characterized in that the structured surface of the membrane ( 2 , 41 ) is implemented as a grid-form netted surface.
6. Measuring cell as claimed in claim 1 , characterized in that the structure is worked into the membrane material.
7. Measuring cell as claimed in claim 1 , characterized in that onto the membrane surface ( 41 a ) at least one layer is deposited which is structured, and that the layer material is comprised of Al 2 O 3 and/or sapphire.
8. Measuring cell as claimed in claim 1 , characterized in that the structure has steps ( 42 ).
9. Measuring cell as claimed in claim 1 , characterized in that the structure comprises table-form elements ( 44 ), disposed interleaved with at least a second plane with table-form elements ( 44 ) such that a labyrinth-like shielding structure is provided.
10. Measuring cell as claimed in claim 1 , characterized in that the thickness of the structure is in the range of 0.1 μm to 20 μm.
11. Measuring cell as claimed in claim 1 , characterized in that between the connection means ( 5 ) of the measuring vacuum volume ( 9 ) and the medium to be measured a baffle arrangement ( 25 ) is disposed.