What flowmeter is used for micro-flow measurement

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This small series to talk about the small flow of the material must be measured with what kind of flowmeter.

There are many kinds of common flowmeters suitable for measuring micro, such as differential pressure type, float type, volumetric type, etc., in which some flowmeters are suitable for measuring both large flow and micro flow, while others are designed for measuring micro flow.

What flowmeter is used for micro-flow measurement

1. Differential pressure flowmeter

 

Differential pressure flowmeters, which consist of standard throttling devices and differential pressure flowmeters, are restricted by three levels in small flow measurements.

 

The limit is the size of the pipe diameter.The standard throttling device is applicable to 50mm and about 50mm pipe diameter.If the pipe diameter is too long, the diameter of throttling device is relatively reduced, it is difficult to carry out similar production and processing as required in the specification.

 

The second constraint is that the gas pressure is very small.This gas pressure is proportional to the square meters of water flow, when the water flow is low enough to a certain standard value, the gas pressure is less and less, so that it is impossible to distinguish.

 

The third limit is the limit of the lower limit of Reynolds number.Different types of throttling devices have different Reynolds number low limits. In general, Reynolds number ≥104 is the applicable limit.The mean water flow and the flow are the low limits of small flow.Since the Reynolds number is very small, the discharge index will change significantly with the change of the Reynolds number, leading to the expansion of the uncertainty.

 

Float flowmeter

 

The key of float flowmeter consists of float and conical tube.The cone tube in the glass tube float flowmeter is glass tube;The tapered tube of the metal hose float flowmeter is made of metal materials, with the hydrodynamic temperature reaching 180℃ and the working pressure of the fluid mechanics reaching 13MPa.

 

The float flowmeter belongs to the light instrument panel. The base deviation of the metal float flowmeter is 1% ~ 2.5% FS for the local labeled type and 1% ~ 4% FS for the far transmitted type.The diameter glass tube float flowmeter is 2.5% ~ 5% FS.Therefore, it is generally only applicable to flow monitoring, but not to carry forward metrological verification.

 

The glass tube float flowmeter is only suitable for vapors and liquids with higher definition, otherwise the height to width ratio of the float in the conical tube is not easy to recognize.The metal hose float flowmeter does not have a limit.

 

The flow-measuring range of the calibre float flowmeter has long been small, with water ranging from 0.3 to 3L/h and gas ranging from 5 to 50L/h.Ecological environmental protection has been used a lot of atmospheric sampler, step free online analyzer and laboratory analyzer and other widely used small laminated glass float flowmeter, its measurement scope can be smaller.

 

In the whole process of industrial production of the level meter, flow, relative density measurement, if the measured material viscosity is very large or corrosion.The common way of blowing gas inspection or blowing liquid to carry out the protection, blowing gas inspection, blowing fluid flow common float flowmeter measurement.In the gas (liquid) source working pressure fluctuation is very big or the place where the measured material working pressure fluctuation is very big, in order to make blowing gas inspection, blowing fluid flow steady and accurate measurement, some commodities float flowmeter and controller (constant current device) with a set of constant gas pressure flow controller.

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