A vacuum gauge is a pressure gauge of measurement in the lower vacuum range than the atmosphere. There are various barometers, some using mercury columns and others using semiconductors.
Vacuum means a space in a state of pressure lower than normal atmospheric pressure. Depending on the range of vacuum (atmospheric pressure), the vacuum is classified into four levels: low vacuum, medium vacuum, high vacuum, and ultra-high vacuum. Ultrahigh vacuum is the highest vacuum with the fewest gas molecules in space.

The vacuum measurement has three methods: mechanical, gas transport, and ionization. The pressure range and vacuum usage of measurement are different according to the measurement methods.

Vacuum Gauge Measurement Range
Type Pressure range (Pa)
Pirani vacuum gauge 104 to 10-1
Capacitance manometer Atmospheric pressure (105) to 10-2
Bayard-Alpert hot-cathode ionization gauge 10-1 to 10-6
Cold-cathode ionization vacuum gauge (Penning vacuum gauge) 1 to 10-3
Spinning rotor vacuum gauges 1 to 10-4

Pirani vacuum gauge consists of a metal filament inside a tube that is heated by electric current using the change in electrical resistance or thermocouples. It is based on the property where gas is proportional to its pressure under low pressure. The air pressure (degree of vacuum) is obtained by measuring the temperature change of the metal filament.

Related Words:
  • Vacuum gauge
  • Pirani vacuum gauge
  • Capacitance manometer
  • Bayard-Alpert hot-cathode ionization gauge
  • Cold-cathode ionization vacuum gauge (Penning vacuum gauge)
  • Spinning rotor vacuum gauge
  • Piezo vacuum gauge
  • Ionization vacuum gauge
  • Cold cathode
  • Hot cathode