Mass Flow Meter Mass flow meters applying the principle of Coriolis force to measure the flow are high-tech products, which are divided into digital and analog circuit mass flow meters (hereinafter referred to as flow meter).
Flowmeter is widely used for process testing and custody transfer measurement in the industries such as petroleum, petrochemical, shipbuilding, pharmacy, municipal administration, paper making, food and energy. As a new kind of relatively advanced and fast developing measuring instrument, it has been attached much importance and accepted by many customers at home and abroad.
Principle It is designed according to the principle of Coriolis force. That is to say, objects will be affected by the force of vector product proportional to moving linear speed and rotating angular velocity. Using the magnet and coil components installed on the measuring tube, two parallel measuring tubes vibrate according to a fixed frequency under the alternating current effect. Once there is flow passing through the pipes, Coriolis force will result in the phase shift of two pipes' vibration and the deflection of vibration is directly proportional to the mass flow of fluid. The mass flow rate could be calculated by testing the vibrating phase shift of two measuring tubes.
The vibration frequency of measuring tube depends on the total mass of measuring tube and inner fluid. It changes correspondingly when the fluid density changes. As a result, the fluid density can be known.
The temperature transducer installed in the pipeline can pick up the fluid temperature on time under the coordination of measuring circuit.
Feature of Digital Circuit Mass Flowmeter
Taking DSP chip as the core, digital circuit mass flowmeter applies the digital signal processing technique developed by the domestic well-known colleges and universities joint. Compared with the traditional product, this highly improves the measuring accuracy and broadens the range ratio. Meanwhile, as digital transmitter calculates more data sampling rate, it can response to flow changes more quickly in a shorter time especially for small batch of canning. Another important advantage to apply DSP is that it can better filter the flow signal by remove the influence of EMF, space electromagnetic field and the on-site noise and therefore makes mass flowmeter more stable and reliable.
Feature of Flowmeter
Comparing with the traditional one, it has the following obvious merits:
Enable to directly measure mass flow rate of fluid in the pipeline without changing any parameters, which avoids some measuring error of intermediate links. It can measure mass flow with high accuracy and good repeatability within bigger range of turndown ratio.
Fluid measured can be more extensive, like the uniform fluid of general viscosity and high viscosity, non-Newtonian fluid. Under a certain condition, slurry containing some solid components and the liquid containing some trace of gas can be counted in.
Measuring tube can be regarded as non-moving parts because of its small vibration. There is no block and moving part inside the pipeline, so it is reliable to enhance the lifetime and reduce the maintenance of flowmeter.
Flowmeter is a multifunctional instrument that can measure not only the mass flow but also the density and temperature. Furthermore, even solute consistency derived from flow and density can also be picked up and output.
Thanks to DSP, high-frequency signal in measurement becomes possible and mass flowmeter of microbend type makes its first appearance. Compared with the traditional one, it has the advantages of less pressure loss, larger flow range and better stability and reliability.
Flowmeter for measuring gas
Early VMZ mass flowmeter was mainly used in liquid measurement, having limited functionality in measuring gas, but it has made great progress in terms of sensitivity and anti-jamming with the improvement of production technology and the usage of VMZ digital circuit. Now, VMZ digital circuit mass flowmeter has been able to accurately measure gas in a very wide range of flow rate.
VMZ digital circuit mass flowmeter still directly measures the mass flow rate of the gas with high accuracy when measuring gas. Besides, based on coriolis force effect, it is related to the structure characteristics and gas mass flow of the flowmeter but it is not influenced by the density, temperature, pressure and other factors of gas medium. Therefore, it is especially applicable on occasions of measuring the mass of the gas.
Second, since VMZ digital circuit mass flowmeter directly measures the mass of the gas flow, it can get the standard volume of gas medium of fixed components through a simple calculation by being introduced the data of density under the standard state (0 ºC and 101.325 kPa) without temperature and pressure compensation. This method can get standard volume data with high precision, and is widely used in most countries in the world. It is an obviously different and great advantage, compared to measuring standard volume of gas medium by using positive displacement, speed flowmeters.
Applications The flowmeter is designed to measure the mass and volume flow, density, mass and volume of liquids, and use the gathered information for technological purposes or commercial accounting. The flowmeter is used as the counter of gasoline, liquefied petroleum gas, kerosene, diesel fuel, oil, oil-water and other liquids in the chemical, petrochemical, oil, food, pharmaceutical and other industries and public municipal facilities. The flowmeter is used in technological processes automatic monitoring and control systems in various industries, for stationary technological plants, land mobile refueling and pumping equipment, and in commercial accounting systems. The flowmeter is designed for use in explosive safe and explosive environment.
Specifications
Nominal Diameter (mm) : 8~300 Measuring Medium: fluid, gas Structure: Integrate -50~125ºC Separate -50~200ºC High Temperature Seperate-50~300ºC Sensor: U series, Microbend series Transmitter: general type, digital type Explosion-proof: General type Explosion-proof Power supply: 24V DC 220V AC Output interface : RS485 Nominal pressure: 1.6, 2.5, 4.0, 6.4 Output signal: pulse signal, (4-20Ma) signal Accuracy: ±0.1% ±0.15% ±0.2% ±0.5% Process connection: GB/T 9115.1-2000, can be customized
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