Vacuum Gauges

A vacuum gauge is used to measure the pressure in a vacuum, which is broadly divided into two categories: high and low vacuum (and sometimes ultra-high vacuum). Many of the different techniques used to measure these categories have an overlap at some point in the pressure range. more...

By combining several different types of gauge it is possible measure system pressure from 10mbar down to 10e-11mbar.

Pumps used as gauges

Turbopump

Make the output a dead end and measure current for a given rotations/s

Membrane pump

Measure membrane displacement to measure the pressure difference between to spaces

Ion getter pump

The gauge is named Penning gauge. Measure the current.

Vacuum gauges are not related to pumps

Thermistor element

Apply a given voltage to a wire into vacuum. The higher the pressure the better the cooling the lower the resistance the higher current.

Ion vacuum gauge

Cathode

It is small to reduce heat radiation. To emit lots of electrons

• it is made of low work function material
• surrounded by anode wires producing a strong, local (as not to catch ions) field

Anode

Thin wires, so that the electrons travel a long path, before hitting them, and instead hit a free atom, knocking one electron of and thus producing a positive ion, which flies to the collector.

Collector

which to emit no electrons is

• small (to reduce the chance to be hit by a photon),
• made of high work function material
• surrounded by anode wires producing a weak, global (as to catch many ions) field

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