How does a gas mass flow meter work?

 

The gas mass flowmeter is not affected by temperature and pressure changes, and its display reading directly indicates the mass flow rate of the gas. It is applicable to a wide range of measurement ranges, and can be used in small flow places in the laboratory and large-scale devices in factory production.

 

Working principle of gas mass flow controller

 

Gas mass flowmeter is a kind of thermal conductivity instrument. At present, many countries have industrial products of this kind of meteor meter. Although the specific structure is different, their working principle is basically the same.

 

The basic principle of this gas mass flowmeter is to wrap four symmetrically on the outer wall of a thin-walled metal tube with a small diameter (4mm) (usually stainless steel, pure nickel or Monel and other corrosion-resistant alloys). A group of resistance wires are connected to each other to form a Wheatstone bridge.

 

As far as the ideal gas is concerned, the specific heat of the gas is a constant value that does not change with the pressure, so the output signal is only positive to the mass flow rate of the gas. The specific heat of a general real gas is affected by the pressure in a small range, so the output signal can still be used to directly represent the mass flow. Think it has nothing to do with the size of the pressure. In practice, because it is difficult to measure the quality of gas to calibrate the instrument, it is often converted into the gas volume (in "standard liter" or standard cubic meter) under the standard state (760 mm Hg, 0 ° C or 760 mm Hg, 20 ° C) "Indicates) to indicate the mass of the gas.