MFC stands for mass flow controller, which means mass flow control. When the fluid flows in the rotating pipe, it will produce a force on the pipe wall. This force was discovered by Coriolis when he studied the hydraulic turbine in 1832, which is called Coriolis force for short. Mass flowmeter is based on Coriolis force. There are two parallel T-shaped vibrating tubes in the sensor, with a driving coil in the middle and vibration pickup coils at both ends. When the excitation voltage provided by the transmitter is applied to the driving coil, the vibrating tube vibrates in a reciprocating cycle, and the fluid medium in the industrial process flows through the vibrating tube of the sensor, which will produce Coriolis force effect on the vibrating tube and make the two vibrating tubes torsional vibration. The vibration pickup coils installed at both ends of the vibrating tube will produce two sets of signals with different phases, which are different from the signals flowing through the sensor. The computer calculates the mass flow through the vibrating tube. When different media flow through the sensor, the main vibration frequency of the vibrating tube is different, and the media density is calculated accordingly. The platinum resistor installed on the vibrating tube of the sensor can indirectly measure the temperature of the medium.
The mass flowmeter directly measures the mass flow of the medium passing through the flowmeter, and can also measure the density of the medium and indirectly measure the temperature of the medium. Because the transmitter is an intelligent instrument with single chip microcomputer as the core, more than ten parameters can be derived from the above three basic quantities for users to use. Mass flowmeter is a new generation flowmeter with flexible configuration, powerful function and high cost performance.
Flow meter for measuring mass flow in pipeline. When the parameters such as pressure and temperature of the measured fluid change greatly, if only the volume flow is measured, the change of fluid density will bring great measurement error. In positive displacement flowmeter and differential pressure flowmeter, the density of the measured fluid may change by 30%, which will cause the error of flow rate by 30 ~ 40%. With the improvement of automation level, many production processes put forward new requirements for flow measurement. The chemical reaction process is controlled by the quality (not the volume) of raw materials. The heating and cooling effects of steam and air flow are also proportional to the mass flow. Strict control of product quality, accurate cost accounting and fuel quantity control of aircraft and missiles also require accurate mass flow measurement. Therefore, mass flowmeter is an important flow measuring instrument.
Mass flow meters can be divided into two categories: one is direct type, that is, direct output mass flow; The other type is indirect or derived, such as using the combination of ultrasonic flowmeter and densimeter, and then multiplying their outputs to get mass flow.
Direct mass flowmeter There are many kinds of direct mass flowmeter, such as calorimetry, angular momentum, gyro and double impeller.
(1) Main parameters:
Mass flow accuracy: 0.002× flow zero drift
Density measurement accuracy: 0.003g/cm3.
Density measurement range: 0.5~ 1.5g/cm3.
Temperature measuring range:1c
(2) Sensor related data:
Ambient temperature: -40 ~ 60℃
Moderate temperature: -50 ~ 200℃
Explosion-proof type: IB Ⅱ BT3
Related equipment: matching transmitter
(3) Relevant data of transmitter:
Working temperature: 0 ~ 60℃
Relative humidity: less than 95%
Power supply: 220 10% AC, 50 Hz or 24 5% DC, 40 watts.