A flow meter is a tool used to measure a liquid or gas's linear, nonlinear, mass, or volumetric flow rate. Flow meters are referred to by many names, such as flow gauge, flow indicator, liquid meter, flow rate sensor, etc., depending on the particular industry. However, they all measure flow. The measuring devices for liquid are mass flow meter, ultrasonic flowmeter, magnetic flow meter, vortex flow meter, thermal flow meter, water flow meter, etc.