The Pirani Gauge is used to measure low vacuum. In the system tungsten filaments are heated up by passing current through them. As gas molecules interact with the filament, heat is carried away and electrical resistance changes. Therefore if the measured current or voltage can be converted into pressure units.
Diaphragm pump (membrane pump) is an oil-free vacuum pump that is used for obtaining #prevacuum of about 0.5 mbar. The pumping in this device is based on the movement of the membrane. As the membrane is pulled down, the volume of the chamber increases, causing a drop of pressure and gas enters the chamber through the inlet. Next, the inlet is closed, outlet opened and the membrane pushed up. This causes the volume of the chamber to decrease and pressure to increase. So the gas is forced to leave the system through the outlet.
The sorption pump is an oil-free #prevacuum pump that is based on the adsorption of gases on cold surfaces. The colder the surface, the more efficient the pumping is! Therefore liquid nitrogen with a temperature less than 77 degrees Kelvin is used for cooling the adsorber. The adsorber is a porous zeolite with a very large surface area as the pores have a diameter in the range of a few nanometers (or less). If the pump is full, then it needs to be renewed by degassing, which is basically heating the adsorber so that the gas can remove the pump through the outlet.
Rotary Vane Pump is an oil-based vacuum pump, that can be used to obtain #prevacuum or even medium vacuum (depending on the system). In this device the rotor and vane(s) are in the housing, that is filled with oil. When the gas enters the chamber through the inlet, it gets trapped in the oil and is transported through the working chamber with the help of the rotor and vane(s) to the outlet, where the gas exits the system. The oil acts as a lubricant and also allows the pumping of some corrosive gases, as it protects the metal to some degree. Although this pump is quite fast and efficient for obtaining pre vacuum, it also may contaminate the vacuum system with oil. Therefore the use of oil traps is highly recommended.