Patent ID: 7305888

Claim:
A vacuum measuring cell comprising: a first housing body ( 1 ) made of Al 2 O 3 ceramic or sapphire material; a membrane ( 2 ) made of Al 2 O 3 ceramic or sapphire material and arranged proximate to said first housing body, said membrane being substantially planar and having a peripheral edge, the peripheral edge of said membrane being joined by a first edge seal to said first housing body in such a way that a reference vacuum chamber ( 25 ) is created between said first housing body and said membrane, said membrane having first and second opposing surfaces, the first surface of said membrane facing said first housing body and said first housing body having a surface facing said membrane; a second housing body ( 4 ) made of Al 2 O 3 ceramic or sapphire material and located opposite said membrane ( 2 ), said second housing body ( 4 ) being joined to the peripheral edge of said membrane by a second edge seal, said second housing body together with said membrane forming a measurement vacuum chamber ( 26 ), said housing body including a port ( 5 ) for connecting the vacuum measuring cell to a medium to be measured; said first housing body, said second housing body and said membrane being tightly connected along the peripheral edge of said membrane; and at least in the central area of the first housing body ( 1 ) an optical transparent window ( 33 ) is formed and of this window ( 33 ) at least in the central region of the membrane ( 2 ) the surface ( 31 ) of the membrane ( 2 ) is formed optically reflective; and wherein, outside of the reference vacuum chamber ( 25 ) in opposition to and at a distance from the window ( 33 ), an optical fibre ( 37 ) is arranged for feeding in and out light onto the surface ( 31 ) of the membrane ( 2 ) and that a lens ( 35 ) is placed between the optical fibre ( 37 ) and the window ( 33 ) for optical linking to the surface ( 31 ) of the membrane ( 2 ) in such a way that the arrangement is forming a measuring section for determining the level of deflection of the membrane ( 2 ) by detecting with a Fabry-Perot Interferometer.