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The fill fluid 52 may be a low TCE fill fluid. For example, the fill fluid 52 may be a combination of a fluid, such as a silicon fluid, and a filler, such as particles having a low TCE. As a more particular example, the fluid of the fill fluid 52 may be silicon polydimethylsiloxane, and the filler may be ceramic oxide particles. As a still more particular example, the fluid may be DC200 supplied by Dow Corning, or DC210H, which is a high temperature fill fluid also supplied by Dow Corning, and the filler may be particles of silicon dioxide.

The filler is added to the fluid to lower the TCE of the fluid. The filler should be mixed with the fluid so that the filler is uniformly distributed throughout the fluid. The filler, for example, may be a fine monodispersed powder having a particle size of around 1 micron. The particles of the filler are preferably, although not necessarily, spherical. The fill fluid 52 may comprise 50% fluid and 50% filler by volume.

The linear thermal expansion coefficient for 316 stainless steel, which can be used for the stainless steel parts described above, may be on the order of 16.5×10-6 m/m/deg C. or a volume thermal expansion coefficient of 50×10-6 m3 /m3 /deg C. The volume thermal expansion coefficient of the fill fluid, DC200H, with no filler is about 950×10-6 m3 /m3 /deg C. The volume thermal expansion coefficient of the fill fluid with filler is about 476×10-6 m3 /m3 /deg C.

Accordingly, the fill fluid 52 has a lower temperature coefficient of expansion (TCE) because of the filler than it would have had without the filler. The fill fluid 52 may have a temperature coefficient of expansion (TCE) that is higher than the TCE of the housing body 14 (as well as relevant other parts, such as stainless steel parts, of the pressure sensor 10). Therefore, as the pressure sensor 10 is exposed to extreme temperatures, the fill fluid 52 does not expand so quickly that plastic deformation of the barrier diaphragm 24 results.




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Note added at 1 hr (2007-10-31 09:05:24 GMT)
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http://www.patentstorm.us/patents/6883378-description.html

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Note added at 1 hr (2007-10-31 09:06:35 GMT)
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