There are two kinds of small flow measurement. One is to measure the gas or liquid flowing through the small pipe with high accuracy.The other is to measure the flow of a very slow fluid.There are many kinds of commonly used gas flow meters suitable for the measurement of micro-flow, such as differential pressure, float, vortex, thermal, etc. Some of them are suitable for the measurement of medium and large flow, but also for the measurement of micro-flow, while others are specially designed for the measurement of micro-flow.
1. Differential pressure flowmeter.The differential pressure flowmeter suitable for measuring small flow rate is mainly the differential pressure flowmeter with inner hole plate.There are some significant differences between this flowmeter and the one with standard throttling device as sensor.The first difference is the structure, the inner hole plate is the sensor and transmitter into one.The second difference is the pipe diameter. The pipe diameter suitable for the inner hole plate is less than 50mm, while the typical pipe inner diameter is 10mm and 20mm.The third difference is the accuracy. The measurement accuracy can be guaranteed by the method of real flow calibration for the inner hole plate, and the accuracy of 1.5 level can be achieved by the real flow calibration.
2. Float flowmeter.Float flowmeter can also be called rotameter, according to the material classification is mainly glass tube float flowmeter, metal tube float flowmeter.With the advantages of small pressure loss and large measuring range, the float flowmeter has become a kind of flow measuring instrument commonly used in industrial control. It is not only easy to use, but also has the advantages of strong compatibility.Especially suitable for the measurement of medium flow with low flow rate and small flow rate.The float flowmeter has the characteristics of simple structure, intuitionistic, low pressure loss and convenient maintenance.The float flowmeter is suitable for measuring the diameter D through the pipe
3. Vortex flowmeter.The precession vortex gas flowmeter works by the precession vortex principle of forced vibration. The precession vortex gas flowmeter is much lower than the flow limit of the vortex flow meter of the same diameter, which is an advantage for measuring small flow gas.The precession vortex gas flowmeter has a wide operating temperature range.Wide range;In a certain Reynolds number range, the fluid temperature, pressure, density and viscosity are not affected.Strong adaptability, in addition to containing larger particles or longer fiber impurities, generally do not need to install filters;Lower requirements for upstream and downstream straight pipe sections, the upstream 4D and the downstream 2D straight pipe sections can be taken;The output frequency is linear with the volume flow rate.
4. Thermal flowmeter.The main characteristics of the thermal gas mass flowmeter: the direct measurement of mass flow without temperature and pressure compensation;Non-contact, no moving parts, low pressure loss, high reliability;Can measure the small gas flow at low flow rate;Gas medium dry clean, no water, oil and other impurities;The hot gas mass flowmeter is also suitable for measuring gas flow in medium and large diameters.