Abstract: A heat loss gauge for measuring gas pressure in an environment includes a resistive sensing element and a resistive compensating element. The resistive compensating element is in circuit with the sensing element and has temperature response and physical characteristics substantially matching those of the resistive sensing element and is exposed to a substantially matching environment. An electrical source is connected to the sensing element for applying current to heat the sensing element relative to the compensating element. Measuring circuitry is connected to the sensing element and the compensating element for determining gas pressure in the environment to which the sensing element and compensating element are exposed based on electrical response of the sensing element and the compensating element.

Abstract: An apparatus for measuring the differential pressure between at least two fluids including (a) first and second pressure enclosures; (b) first and second pressure deformable members where the first deformable member is sealingly connected to the first pressure enclosure and second deformable member is sealingly connected to the second pressure enclosure and the pressure deformable members are rigidly linked so as to move as one unit; (c) a frame for locating the first and second pressure enclosures in fixed relationship to one another; (d) a position sensing device for determining the displacement of the pressure deformable members relative to the frame; (e) a force balancing device including a first portion rigidly connected to the frame and a moveable second portion connected to the pressure deformable members; (f) a transducer for transducing the displacement of the first and second pressure deformable members into a force acting on the moveable second portion of the force balancing device in a direction t

Abstract: An improved Pirani gauge has a small-diameter wire sensing element, coplanar with a small-diameter wire compensating element, with two parallel flat thermally conductive plates spaced from the sensing and compensating elements. The sensing and compensating elements and their connections have the same physical dimensions, thermal properties and resistance properties. The connections have large thermal conductances to a uniform temperature region and the elements are located in the same vacuum environment. A DC heating current is used and confined to only the sensing element. A relatively small AC signal is used to sense bridge balance. A simplified three-dimensional pressure compensation formula provides accurate compensation while simplifying the collection of calibration data. The improved gauge provides significant advancements in Pirani gauge accuracy, production cost, and package size.

Abstract: An ionization gauge including a source of electrons; an open anode defining an anode volume, where the source of electrons is disposed outside the anode volume; a plurality of ion collector electrodes disposed within the anode volume; a plurality of axially extending anode support posts for supporting the open anode, the anode support posts being electrically connected to the open anode; and the plurality of ion collector electrodes being respectively located sufficiently close to the plurality of axially extending anode support posts so as to substantially repel the electrons from the anode support posts.

Abstract: Controller circuitry and method for controlling the operation of an ionization gauge having a source of electrons, an anode, an ion collector electrode. Circuitry is provided (a) for providing an electron emission current from the electron source (b) for measuring the heating power W.sub.X of the electron source to obtain a measured value of the heating power at an unknown pressure P.sub.X and (c) measuring the ion current to the collector electrode to obtain a measured value of the positive ion current i.sub.+X at the unknown pressure. A memory is also provided for storing at least one equation for pressure, the pressure equation being obtained from a reference gauge by measuring the current i.sub.+cal to the positive ion collector electrode, the electron emission current i.sub.-cal from the electron source and the heating power W.sub.cal of the electron source of the reference gauge at selected calibration pressures P.sub.cal and selected heating powers W.sub.

Abstract: An ionization gauge including a source of electrons; an open anode defining an anode volume, where the source of electrons is disposed outside the anode volume; a plurality of ion collector electrodes disposed within the anode volume; a plurality of axially extending anode support posts for supporting the open anode, the anode support posts being electrically connected to the open anode; and the plurality of ion collector electrodes being respectively located sufficiently close to the plurality of axially extending anode support posts so as to substantially repel the electrons from the anode support posts.

Abstract: An improved Pirani gauge has a small-diameter wire sensing element, coplanar with a small-diameter wire compensating element, with two parallel flat thermally conductive plates spaced from the sensing and compensating elements. The sensing and compensating elements and their connections have the same physical dimensions, thermal properties and resistance properties. The connections have large thermal conductances to a uniform temperature region and the elements are located in the same vacuum environment. A DC heating current is used and confined to only the sensing element. A relatively small AC signal is used to sense bridge balance. A simplified three-dimensional pressure compensation formula provides accurate compensation while simplifying the collection of calibration data. The improved gauge provides significant advancements in Pirani gauge accuracy, production cost, and package size.

Abstract: An ionization gauge including a source of electrons; an open anode defining an anode volume, where the source of electrons is disposed outside the anode volume; a plurality of ion collector electrodes disposed within the anode volume; a plurality of axially extending anode support posts for supporting the open anode, the anode support posts being electrically connected to the open anode; and the plurality of ion collector electrodes being respectively located sufficiently close to the plurality of axially extending anode support posts so as to substantially repel the electrons from the anode support posts.

Abstract: An apparatus for measuring the differential pressure between at least two fluids including (a) first and second pressure enclosures; (b) first and second pressure deformable members where the first deformable member is sealingly connected to the first pressure enclosure and second deformable member is sealingly connected to the second pressure enclosure and the pressure deformable members are rigidly linked so as to move as one unit; (c) a frame for locating the first and second pressure enclosures in fixed relationship to one another; (d) a position sensing device for determining the displacement of the pressure deformable members relative to the frame; (e) a force balancing device including a first portion rigidly connected to the frame and a moveable second portion connected to the pressure deformable members; and (f) a transducer for transducing the displacement of the first and second pressure deformable members into a force acting on the moveable second portion of the force balancing device in a directi

Abstract: Controller circuitry and method for controlling the operation of an ionization gauge having a source of electrons, an anode, an ion collector electrode. Circuitry is provided (a) for providing an electron emission current from the electron source (b) for measuring the heating power W.sub.X of the electron source to obtain a measured value of the heating power at an unknown pressure P.sub.X and (c) measuring the ion current to the collector electrode to obtain a measured value of the positive ion current i.sub.+X at the unknown pressure. A memory is also provided for storing at least one equation for pressure, the pressure equation being obtained from a reference gauge by measuring the current i.sub.+cal to the positive ion collector electrode, the electron emission current i.sub.-cal from the electron source and the heating power W.sub.cal of the electron source of the reference gauge at selected calibration pressures P.sub.cal and selected heating powers W.sub.