Apparatus for measuring the specific gravity of gases

Claim 3

Apparatus as claimed in claim 1, wherein the pressure control means is arranged to maintain the pressure of the gas in the said recess at a value greater than but relatively close to normal atmospheric pressure.

Claim 4

Apparatus as claimed in claim 1, wherein the vibratable member comprises a hollow right cylindrical shell member arranged to have both its internal and external surfaces exposed to the gas in the said recess, and the exciting means is arranged to excite bell-like (hoop mode) vibrations of said cylindrical shell member.

Claim 5

Apparatus for measuring the specific gravity of a gas, comprising: a heat sink member defining a recess and a substantially fixed-volume reservoir for containing a fixed mass of a reference gas, said recess and said reservoir both being disposed inside said heat sink member, an inlet conduit for receiving the gas whose density is to be measured and conducting it into said recess, and an outlet conduit for conducting said gas out of said recess, said inlet conduit, said recess and said reservoir all being in intimate thermal contact with said heat sink member so as to tend to maintain the gas in the recess at substantially the same temperature as the reference gas in the reservoir, said inlet conduit comprising a pipe wound around the outside of said heat sink member in intimate thermal contact therewith, said inlet conduit passing through said heat sink member to said recess, pressure control means responsive to any difference between the pressure of the reference gas and the pressure of the gas in the recess to reduce said difference and tend to equalize said pressures, said pressure control means comprising an outlet valve arranged to control the venting of the gas from the outlet conduit, and a movable diaphragm connected to operate the valve, opposite sides of the diaphragm being subjected to the respective pressures of the reference gas and the gas in the outlet conduit and hence in the recess, and a density-sensitive device disposed in said recess and adapted to produce an output signal representative of the density of the gas flowing through the recess, whereby the density represented by said output signal is proportional to the specific gravity of the gas, said density-sensitive device comprising a vibratable hollow right cylindrical shell member arranged to have both its internal and external surfaces exposed to the gas in the recess, means for exciting the vibratable shell member in bell-like, hoop made vibrations at a natural frequency thereof, and means for producing an output signal representative of said frequency, which signal is also the output signal proportional to the specific gravity of the gas.

Claim 6

Apparatus for measuring the specific gravity of a gas, comprising: a heat sink member defining a recess and a substantially fixed-volume reservoir for containing a fixed mass of a reference gas, said recess and said reservoir both being disposed inside said heat sink member, an inlet conduit for receiving the gas whose density is to be measured and conducting it into said recess, and an outlet conduit for conducting said gas out of said recess, said inlet conduit, said recess and said reservoir all being in intimate thermal contact with said heat sink member so as to tend to maintain the gas in the recess at substantially the same temperature as the reference gas in the reservoir, said inlet conduit comprising a pipe wound around the outside of said heat sink member in intimate thermal contact therewith, said inlet conduit passing through said heat sink member to said recess, pressure control means responsive to any difference between the pressure of the reference gas and the pressure of the gas in the recess to reduce said difference and tend to equalize said pressures, said pressure control means comprising an outlet valve arranged to control the venting of the gas from the outlet conduit, and a movable diaphragm connected to operate the valve, opposite sides of the diaphragm being subjected to the respective pressures of the reference gas and the gas in the outlet conduit and hence in the recess, and a density-sensitive device disposed in said recess and adapted to produce an output signal representative of the density of the gas flowing through the recess, whereby the density represented by said output signal is proportional to the specific gravity of the gas, said density-sensitive device comprising a vibratable hollow right cylindrical shell member arranged to have both its internal and external surfaces exposed to the gas in the recess, means for exciting the vibratable shell member in bell-like, hoop made vibrations at a natural frequency thereof, and means for producing an output signal representative of said frequency, which signal is also the output signal proportional to the specific gravity of the gas.