The National Science and Technology Terminology Review Committee defines a flowmeter as an instrument that indicates the measured flow rate and/or the total amount of fluid within a selected time interval. Simply put, it is an instrument used to measure fluid flow in pipelines or open channels Flow meters are divided into differential pressure flow meters, rotor flow meters, throttling flow meters, narrow slit flow meters, volumetric flow meters, electromagnetic flow meters, ultrasonic flow meters, etc. Classified by medium: liquid flowmeter and gas flowmeter.