These are also known as oscillating piston flowmeters. These are one of the oldest positive displacement type flowmeter designs. These types of meters are mainly of single or multiple-piston types.
Other types available are double acting pistons and rotary pistons. Selection of a particular type of piston meter depends on the range of flow rates necessary for an application.
Although piston meters are smaller in size and considered apt for handling only low flows of viscous liquids, yet they are proficient enough to deal with an extensive range of liquids.
Major application areas of a reciprocating piston meter include viscous fluid services like oil metering on engine test stands, specifically where turndown ratio is not considered much crucial.
Also these meters can be employed on residential water service where they tend to pass partial quantities of dirt and fine sand along with water.