How does an AIM gauge work?
AIM gauges, or ‘Inverted Magnetron’ gauges work by measuring the discharge current generated by a plasma confined between a rod shaped anode and an outer, cylindrical, cathode electrode.... Read More... |
How does a Pirani Gauge work?
The Pirani gauge is used to measure vacuum at low or roughing levels. This method of measuring vacuum was invented in 1906 by Marcello Pirani... Read More... |
Vacuum Gauges
Gauges are an important part of any vacuum system, they indicate what is happening in the system and give information on how much gas is left inside it.
When producing a vacuum we are reducing the number of gas molecules, usually air, in the system. Gauges indicate how much gas remains and hence the pressure in the system under specific conditions. We may wish to know the pressure in the system for quality control reasons to make sure that a process is repeated under the same conditions.
Because it is not possible to individually count the number of gas molecules inside the vacuum system we have to use a physical property of the gas to give us an indirect estimate. Because of the different gas properties used to measure the pressure inside a vacuum system we require a range of different types of gauges, which rely on physical processes for their action. There are three main groups of gauges:
Mechanical: Those that measure Force by movement of a flexible surface e.g. the Capsule Dial gauge, Strain gauge or Capacitance Manometer.
Thermal: Those that measure energy (heat) transfer such as the Thermocouple or Pirani gauge.
Electrical: Those that measure the electrical conductivity of the gas such as the Inverted Magnetron and hot cathode Ionisation gauge.
A gauge should be chosen that is appropriate for the process that it will be monitoring.
The operating pressure range of your vacuum system will help you to determine what type of gauge can be used.
Measurement made by mechanical gauges (dial gauges, strain gauges and capacitance manometers) are not affected by gas type whereas the other gauges will give a reading which is dependent on the gas species it is measuring. With non-mechanical gauges, pressure readings will change if the gas type changes, for example Argon, Helium, Oxygen, Nitrogen, etc. So when choosing a non-mechanical vacuum gauge, consideration needs to be given to what type(s) of gas is/are being used within the system.
Choice may also be influenced by the degree of accuracy that is required, or whether the gauge will withstand attack by process gases that it is exposed to.
AVT can help you decide exactly which gauge is right for you, considering your application and affordability. Contact us and let us know your requirements.