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Introduction
F*6 Metal Tube Variable area Flow meter Series are used for measure instantaneous and accumulated flow rate of liquid, gas and steam in closed pipelines. It is suitable for metering flow value on site or electronic remote. The measuring principle is based on the hydrodynamic effects,This makes float moving from bottom to top in vertical Pipe. As the displacement of float is in related to flow rate, which can be read from the indicator by means of the magnetic drive system in non-contact form . Also, flowmeters output electrical signal (***0)mA / hart communication protocol with high / low limit Warning switches/integrating flow PCB broad can be configured.

Operating principle
F*6 series variable area flowmeters is made up of flow sensor and flow indicator. Float is placed vertically inside of conical measuring tube and can freely move up and down along the conical tube owing to hydrodynamic effects.A high-performance permanent magnet is set inside float, by this way the magnetic field around permanent magnet will change along with the float moving up and down.When fluid keeps a stable flow value and float locates in a dynamic balance state in position, the magnetic field around permanent magnet keeps constant also.The magnetic signal will be transmitted in non-contact form by means of the flow Indicator mechanically connected to conical tube. In another word,the indicator is able to detect and process flow value of liquid by magnetic drive system and finally the corresponding flow rate value can be read from the scale on site. Also it can indicate outputs as standard electrical signal (***0)mA / hart communication protocol.

Measurement of gases
When the valve is opened suddenly in pipeline or pressure is unstable during metering gases, airflow will be pulsating. As a result, float moves up and down along the conical tube ceaselessly. In the meantime, system is out-of-control since pointer swinging constantly lead to output signal instability. In this conditions,damping device must be installed inside measuring tube (see fig.**2). The damping device become a self-centering damper of preventing block through special design and precision work of numerical control machine centre. The damping device is consists of aluminum oxide ceramic (purity is *9.*9%) and characterized by a long service life, resistant to corrosion, structure novelty, practicality better.