Abstract: A Bayard-Alpert gas pressure measuring gauge with x-ray effect neutralization comprising collector and shield electrodes that comprise the same substantially inert electrically conductive substances. Said inert substance may be gold or another substance from the group consisting of platinum and rhodium, and mixtures thereof, and alloys comprising gold, platinum or rhodium; or said substance may be selected from the group consisting of the oxides of indium, chromium, vanadium and tin, mixtures thereof, and alloys comprising one of these. An electrical potential is applied to the shield that is more negative than the potential applied to the collector, said potential on the shield being in the range from about zero volts to about −50 volts when the collector is operated at a positive potential. Said negative potential with respect to the collector enhances the reverse x-ray effect for cancellation of the forward x-ray effect in the gauge.

Abstract: A cold cathode ionization gauge includes a first and second electrode spaced apart and insulated from one another and having a common axis. A magnetic field generator surrounds the gauge and applies a non-time varying magnetic field along the common axis of the electrodes. The magnetic field generator includes at least one pair of opposed axially magnetized magnets adjacent each other. In one embodiment of the invention a non-magnetic annular spacer is placed between the opposed magnets. The magnet arrangement minimizes magnetic flux outside of the gauge while increasing the strength of the magnetic flux inside of the gauge. The magnetic arrangement also allows the gauge to be ignited in a very high vacuum, thereby extending the operating range of the gauge.

Abstract: A thermocouple vacuum gauge includes a first thermocouple element spaced below a second thermocouple element. The two thermocouple elements are electrically connected in series in a back-to-back manner by connecting together their respective negative ends. A pulse generator supplies a pulsing on-off current only to the first thermocouple element. During the off intervals, a switch connects the positive ends of both thermocouple elements to a voltage measuring and comparing circuit which measures a thermally generated voltage signal between the positive ends of the thermocouple elements and compares the measured voltage signal to a reference signal. The result of the comparison is used to vary the output current of the pulse generator so as to supply an amount of current to the first thermocouple element sufficient to cause the measured voltage signal to approach the reference signal.