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There are many types of flow measurement instruments, commonly known as flowmeters, and they vary in measurement principles and application ranges. Below is a brief introduction to some of the most commonly used flow measurement instruments. 1. Thermal mass flow meter The thermal mass flow meter measures the fluid velocity by detecting the increase in the fluid’s temperature or the decrease in the temperature of a heat sensor. A thermal mass flow meter has no moving parts or orifices, and can accurately measure gas flow rates. The thermal mass flow meter is one of the few technologies capable of measuring mass flow rate, and it is also one of the few technologies used for measuring gas flow rates in large diameters. 2. Vortex flow meter: A vortex flow meter involves placing a non-streamlined vortex generator in the fluid; the speed of the vortices is proportional to the speed of the fluid, which allows for the calculation of the volume flow rate. Vortex flowmeters are suitable for measuring liquids, gases, or steam. It has no moving parts, nor are there any issues with dirt. Vortex flow meters generate noise, and they require a high flow velocity of the fluid in order to create vortices. 3. Ultrasonic flow meters The time-of-flight method and the Doppler effect method are commonly used in ultrasonic flow meters to measure the average velocity of fluids. Like other flow meters, it is a device for measuring volumetric flow rate. It is a non-obstructing flow meter; if the ultrasonic transmitter is installed on the outside of the pipe, there is no need to insert it. It is suitable for almost all liquids, including slurries, and offers high precision. However, dirt in the pipes can affect accuracy. 4. Turbine flowmeter: When fluid flows through a turbine flowmeter, it causes the rotor to rotate. The rotational speed of the rotor is related to the velocity of the fluid. The flow rate or total volume is derived from the average fluid velocity sensed by the rotor. Turbine flowmeters can accurately measure clean liquids and gases. Like volume flowmeters, turbine flowmeters also suffer from irreversible pressure errors and require moving parts as well. 5. Electromagnetic flowmeter: An electromagnetic flowmeter measures the velocity of a conductive fluid as it flows through an electromagnetic field, by detecting the voltage generated. Electromagnetic flowmeters have no moving parts and are not affected by the fluid. The accuracy of measuring conductive liquids when the tube is full is very high. Electromagnetic flowmeters can be used to measure the flow rate of slurry-like fluids. 6. Differential pressure flow meters Differential pressure flow meters are the most common type of flow measurement technology, including orifice plate flow meters, V-cone flow meters, venturi tubes, and sonic nozzles. Differential pressure flowmeters can be used to measure the flow rate of most liquids, gases, and vapors. Differential pressure flowmeters have no moving parts, are widely used, and are easy to operate. But after getting clogged, it causes pressure loss, affecting accuracy. The accuracy of flow measurement depends on the accuracy of the pressure transmitter. Flow metering is one of the components of metrological science and technology, and it is closely related to the national economy, national defense construction, and scientific research. Flow metering is widely used in various fields such as industrial and agricultural production, national defense construction, scientific research, foreign trade, and people’s daily lives.