Manometer system for monitoring pressure in a particle study device

Claim 1

A manometer system particularly adapted for monitoring pressure in a particle study device which includes a first vessel with fluid therein, a smaller second vessel with fluid therein, an aperture through the wall of the second vessel, and means for applying a vacuum or pressure to the second vessel to cause relative fluid flow between the first vessel and the second vessel through the aperture, said manometer system including a generally vertically disposed, U-shaped manometer forming tubing having a first leg, a second leg and a bight portion therebetween said first leg being connected to said vacuum applying means, a portion of said second leg having an enlarged cross-section, the remaining portion of said second leg above said enlarged crosssection portion being of reduced cross-section and including a pressure indicating section, the free end of said second leg being vented to atmosphere, said tubing being partially filled with mercury with the meniscus of mercury in said second leg being located in said enlarged cross-section portion, a lightweight fluid in said second leg above said mercury, the meniscus of said lightweight fluid being situated in said pressure indicating section such that changes in pressure against the meniscus of mercury in said first leg which causes a change in the height of the meniscus in said second leg will cause a much larger change in the height of the meniscus of said lightweight fluid by reason of the difference in volume between the enlarged cross-section portion and the indicating section, and means above said indicating section for throttling fluid flow through said tubing, said throttling means serving to dampen movement of said lightweight fluid and to prevent rapid escape of lightweight fluid and mercury if a sudden increase in pressure is applied to the mercury meniscus in said first leg.