Mechanical flow measurement devices

Flow measuring devices can be primarily classified based on the type of flow measurement – eithermassflow measurement or volumetric flow measurement. The flow measurement devices can also be further classified based on their principle of operation. Here a list and brief explanation of commonly used flow measurement devices is presented.

Mechanical flow measurement devices

Piston flow meteroperates on the principle of a piston oscillating within a casing of known volume. For each oscillation, a fixed amount of fluid passes through the piston casing. Through a gears connected to this piston the flow meter dial is used to count the number of piston oscillations thus total fluid that has passed through in a given time period is know. This volume divided by the time gives volumetric flow rate. Piston flow meters are commonly used for domestic water usage measurement.

Oval gear flow meter是另一个积极的位移类型流量计。该流量计使用两个或更多的长方形齿轮，配置为以直角旋转，形成T形。这种布置允许在流量计室中形成两个部分，它们彼此完全密封，就像椭圆形齿轮类型的正置位移泵中的部分一样。因此，齿轮的每个旋转都对应于通过流量计的固定流体体积。因此，可以通过监视齿轮旋转次数来测量流量和通过仪表的体积。

Rotameter / Variable area meterconsists of a vertical tapered glass tube and a float inside the tube.The arrangement of tapered tube and float is such that the float is pushed up by the increase in flow due to higher pressure and viscous forces and the float is pulled down by gravity if the flowrate decreases. The rotameter is calibrated to be used for a specific service, typically water or air.

Turbine flow metersutilize a turbine wheel for the measurement of flow, as the name suggests. This turbine wheel sent in the path of fluid flow rotates, assisted by the fluid hitting the turbine blades. Speed of rotation is proportional to fluid velocity hitting the turbine blades and the flow meter is calibrated accordingly to accurately measure the flow. They are commonly used in fire water systems and other water distribution systems.

Single jet flow meter and Paddle wheel flow meteruse a mechanism similar to turbine flow meters and consist of a simple impeller wheel with radial vanes, impinged upon by a single jet. For paddle wheel flow meters the wheel blades are smaller in width compared to single jet flow meter and are only partially projected in the path of the flow.

Multiple jet flow meter类似于单射流流量计，除了从多个点扔在叶轮叶片上，从而在涡轮叶片的圆周上击中了多个点。这种布置可最大程度地减少叶轮叶片的磨损。

Pelton wheel flow meter or Radial turbine flow meteruses a radial turbine to convert the fluid flow into speed of rotation for the turbine wheel which is calibrated to measure fluid velocity and fluid flow.

Nutating disc flow meteruses an eccentrically mounted disc which nutates or wobbles when the fluid flow hits the disc. The tilted disc forms a chamber to allow the fluid flow which remains on one side of the disc. Thus one rotation of the disc corresponds to fixed volume that has passed through. This type is the most commonly used flow meter to measure water supply flow rates.