Bayard-Alpert Type Ionization Gauge – Operating Principles

Bayard-Alpert type ionization gauge created a new level of experience in the measurement of gases and pressures within high and ultra high vacuum environments. Its creation improved efficiency and accuracy, opening up vacuum working at these lower pressures and their associated applications to more sectors.

The Bayard Alpert gauge is a hot filament ion gauge. Its primary component is a heated filament, otherwise known as a cathode, that is used to emit electrons towards an anode (the grid). The pressure measurement of the Bayard Alpert vacuum ion gauge is based on the ionization of gas molecules through a continuous flow of electrons. Negative electrons are emitted at a selected, controlled rate from the heated filament. They are accelerated towards the positively charged wire grid, and as they pass into space enclosed by the grid, the electrons strike the gas molecules present in the vacuum system. This produces positive ions. These are gathered by the ion collector, which is at almost ground potential and negative in relation to the grid. Given a constant filament to grid voltage, as well as electron emission current, then the positive ion formation rate is directly proportionate to the pressure in the gauge. However, this only holds true for pressure around 1 x 10-3 Torr and below. Pressure indication in the Bayard Alpert ion gauge is linear, and this is one of the reasons why it is considered to be the most accurate continuous indicator of high and UHV level pressures.

At Arun Microelectronics Limited, we manufacture Bayard-Alpert type ionization gauges alongside a wide range of compatible parts and accessories. This includes the ion gauge controller and ion gauge cables to complete your vacuum system. Our team of engineers are always on hand to answer your questions and can be reached through the contact page of our website at