How do mass flow meters and flow controllers work?

Thermal mass flow meter basics

Thermal gas mass flow meters are flow meters designed based on the principle of thermal diffusion. That is to say, when the fluid flows through the heating object, the heat dissipation of the heating object is proportional to the flow rate of the fluid. The sensor of this series of flowmeters has two standard RTDs, one is used as a heat source and the other is used to measure the fluid temperature. When the fluid flows, the temperature difference between the two is linearly related to the flow rate. Through microelectronic control technology, this relationship is converted into a linear output of the measured flow signal. 

How to distinguish between thermal flow meter controllers and mass flow meters?

The thermal gas mass flow controller is composed of a flow sensor, a diverter channel, a flow regulating valve and an amplifier controller. The gas flow sensor uses the principle of capillary heat transfer thermocalorimetry to measure the mass flow of gas (without temperature and pressure compensation). The flow signal measured by the sensor heating bridge is sent to the amplifier for amplification, the amplified flow detection voltage is compared with the set voltage, and then the difference signal is amplified to control the regulating valve, and the closed-loop control of the flow through the channel to make it equal to The set flow is equal. The diverter determines the flow of the main channel. The flow display instrument matched with the mass flow controller is equipped with a regulated power supply, a digital voltmeter, a setting potentiometer, peripherals, built-in conversion and three-position valve-controlled switches.

Thermal mass flowmeters controller application in life

The further improvement of the use effect of the mass flow controller and the improvement of the convenience have fundamentally been able to complete the implementation of effective specific application regulations, but it is still necessary to start with the daily standards in all aspects to ensure the achievement of standardized and purposeful applications, so as to improve Further sound completion of the application for the significant advantages of the targeted mass flow controller in the production process is truly a service guarantee for standardizing the production process.

These actions of scientific experiments must ensure the rational use of resources, which means that resources cannot be ignored and disappeared when applying resources. The resources that exist in society are always in short supply, and people's requirements for resources are constant. Therefore, how to solve the relatively limited resources in a certain way and then obtain the optimal allocation is the problem that everyone faces.

In winter, the temperature difference between day and night is very large, and it can even reach minus 20 degrees at night. If it is dealt with in terms of model selection, it is very uneconomical, and the choice of thermal insulation, electric heat tracing, maintenance (point safety inspection, sewage treatment), etc. The way is the solution for cold protection. The data signal of the flowmeter is transmitted far to the water meter instrument panel, indicating that the meter head should consider the environmental temperature resistance regulations, and the isolation fluid should consider the environmental temperature resistance regulations of the isolation fluid.

Therefore, in the actual operation process, the evaluation of the mass flow controller stipulates that the corresponding environmental factors should be well controlled in advance. In particular, it is necessary to master the relevant content between the natural environment and the hazards of the mass flow controller, so as to ensure the full play of the mass flow controller in the specified natural environment.

The use of general mass flow meters

Thermal mass flow meters are generally used to monitor or manipulate the whole process related to quality, such as chemical changes that do not reflect the relative quality of components, such as secret recipes, clear raw material balance, tax invoices and actual operations of import and export trade work. Because these are very important total flow measurements in manufacturing plants, the stability and accuracy of gas flow measurement is very important.

Thermal mass flow meters are typically used to monitor or manipulate quality-related processes, such as chemical changes that do not reflect the relative masses of components. Measurements are not compromised by operating pressure and/or temperature shifts when verifying gas flow rates for compressible steam and exhaust gases. One of the functions of thermal mass flow meters is to measure low gas flow rates or low gas flow rates (under 25 inches per minute), far less than all other devices can check.

The mass flow controller is based on the Coriolis basic principle of vibration when the fluid flows through the pipeline to achieve accurate measurement purposes. Therefore, the installation of the mass flowmeter should be in a stress-free state, and the installation of the steam flowmeter should be in the same center as the pipeline. It should be used as a support point around the mass flow meter sensor, and the sensor cannot be used to support the point pipeline, which can remove vibration and reduce deviation.

The selected installation location should avoid large transformers or motors. Because the cable between the sensor and the pressure transmitter is covered or approached by the magnetic field emitted by the motor, for example, it will cause influence and make the reading value inaccurate and cause deviation. Also, during installation, different orientations of the installation house should be selected according to the different characteristics of the fluid, that is, it is necessary to keep the fluid in the sensor pipeline continuously flooded.

Carry bubbles. When used for liquid flow measurement, the mass flowmeter will stop working when the mist-like vapor content exceeds 1% to 5% of the volume content. This bubble dissipates the vibration of the total flow tube that is used to create the Coriolis force, which should be purged before the sensor. If it is difficult to achieve, try to reduce the gas content (try to increase the working pressure in the sensor) to ensure that the bubbles are evenly dispersed into smaller bubbles (to ensure a higher liquid flow rate).