Research On Low Flow Velocity Measurement Based On Magnetic Field Detection Of Hall Sensor

In the research fields such as micro/nano manufacturing, chemistry and chemical engineering,biological sensor inspection and clinical medicine, often need to detection and control the rate of flow and flow velocity of the fluid flow accurately. According to the different applications and different detection principle,People have designed various of sensor to detect flow velocity, however, there is high dimensional coupling between the size effect of flow channel structuret, the physical and electrical properties of the sensor when the flow velocity is low. The shortcoming of using the traditional method to detect the low velocity are having large detection error and high cost.Therefore, how to detect the low velocity precisely become the hot spot in flow velocity research.In this paper, we have studied the changing rule of magnetic field intensity when the magnetic rotor through the examine position of linear hall sensor, and based on the theoretical analysis and the detection principle of linear hall sensor in magnetic field strength detection,we proposed a new kind of flow sensor, the experimental results show that compared with the hall switch velocity sensors, the new sensor has higher accuracy in low velocity detection of fluid.First of all,we studied the changing law of magnetic intensity in volumetric velocity sensor when the magnetic rotor through the examine position, and according to the space geometry change law and the distribution of the magnetic field intensity,we deduced the relationship between the rotor speed and magnetic intensity of the examine position.we also built up a mathematics theory model between hall voltage, magnetic field intensity, the angular velocity of rotor, rotational speed and flow rate, the theoretical research show that there is a linear relationship between the angular velocity of rotor and the change of magnetic intensity at the examine position.Secondly, using linear hall sensor detect the changes of the magnetic field strength, and based on the mathematics theory model between angular velocity of rotor and the change of magnetic field intensity, using The least squares fitting methods to calculate the angular velocity of rotor.and designed a velocity detection system to realize the automatic calculation and display of the angular velocity based on 51 single-chip microcomputer.Finally, designed two experiments,one is to detect the magnetic intensity in different flow velocity and the other is to detect the flow velocity with our low velocity detection system. the experimental results show that compared with traditional switch type velocity sensor, this paper puts forward the low velocity detection method can detect the lower fluid velocity, has the characteristics of simple structure, high precision.