In practice, we know quite a lot of methods to determine the flow rate. The simplest and therefore the most common of these are methods of using mechanical sensors, in which the flow moves or turns solid. Thus, this movement or rotation of the body is proportional to the flow rate.
Figure 1 shows the basic mechanical methods of flow measurement. In particular, in Figure 1.a, and the spring-loaded and displayed hanging on the hinge arm, which is rejected by opening a hole when the fluid passes through the converter. The higher the rate, the more open the hole, ie the more deflected blade.
Figure 1.b shows the sensor, which uses the same method but with limited spring plug. There may be other kinds of implementation of this method of flow measurement. In the sensor in Figure 1.в, the method is implemented in the propeller rotating in the flow of material. The frequency of rotation of the propeller is proportional to the flow rate of the substance.
The most common mechanical flow transmitter is a turbine meter with a rotating propeller (or in this case the turbine). Turbine installed in the flow of material through the bearings. In general, the turbine blades are made of a ferromagnetic material. Therefore, the coil, mounted on the housing of the flowmeter is used to determine the speed impeller. Electromagnetic flowmeter sensor element has the effect of braking the turbine at low speed flow of the medium may affect the angular velocity of the impeller. Low flow using other designs of sensors, such as electro.
With accurate measurements it is important that there is no turbulence flowing substance, because it directly affects the speed impeller. Therefore, flow straightening vanes, usually set at the entrance of the flowmeter. These blades also form one of the handles impeller. Of course, there may be a much more simple design flow, where accuracy is not essential, that is, when braking and swirl can be ignored.
One of the advantages of turbine flow compared to other types of flow meters is a linear dependence of the output signal from the flow rate in the intended range.