Patent ID: 7443169
Filing Date: 2008-10-28
Classification: C23C,G01L

Abstract:
1. A vacuum measuring cell ( 15 ) with a shield arrangement ( 25 ) for performing a protective function by decreasing contamination of the vacuum measuring cell in order to increase service life of the measuring cell while ensuring high measuring precision and reproducibility of vacuum measurement, the vacuum measuring cell comprising: a measuring cell housing ( 1 , 4 ) with a diaphragm ( 2 ) for measuring a vacuum, a shield housing encompassing a shield, the shield housing being outside the measuring cell housing and having an exit port ( 16 ) with an exit opening connected to the measuring cell housing and a connection opening ( 22 ) for connection with an object space to be measured, and the shield being disposed between the openings ( 16 , 22 ), the shield housing comprising a tubular section ( 14 ) and the shield ( 7 , 20 ) in the tubular section, the shield comprising a screw shield ( 20 ) with spiral convolutions ( 21 ) defining a spiral path with a cross section, the convolutions having at least one thread flange with an outer diameter in contact with an inner wall of the tubular section ( 14 ) so that in an axial line of vision between the openings, the shield is optically tight so as not to permit any through-view between the openings and such that a gas throughflow between the outer diameter of the thread flange and the inner wall is inhibited and such throughflow is forced substantially only into the spiral path, the exit port ( 16 ) being on the one side of the tubular section ( 14 ) and the connection opening ( 22 ) being on the other opposite side of the tubular section, the shield arrangement with its spiral path decreasing contamination of the vacuum measuring cell, and the cross section of the spiral path being larger than a cross section of all solid material of the screw shield so that a favorable ratio of spiral path cross section to solid material cross section is provided for improving the protective function of the shield arrangement and to improve measuring performance of the vacuum measuring cell.