Detecting The Position Of Floating Element With Magnetoresistance Sensors

Rotameter is a kind of classical variable area flow meter, which has many advantages such as simple structure, reliability, low pressure losing and high stability and so on. At the same time, it can be used to measure the fluid medium of low flow rate. According to the material of its taper pipe, two types of rotameter are available: glass tube rotameter and metal tube rotameter, and glass tube rotameter, whose floating element's position can be read directly, is usually used to measure low pressure, normal temperature, without granule suspended substance or opaque fluid. Because it is only used in local place, it doesn't have the functions of transmitting remote signal and measuring high temperature, high pressure or opaque fluid. Therefore, metal tube rotameter is widely used in industrial fields.Two kinds of techniques of measuring the floating element's position of metal tube rotameter, used pure solid sensors and semisolid sensors respectively, are studied on in this paper. A non-contact, little mechanical wearing, high stability and reliability, simple installation and low-power consumption semisolid sensor is developed successfully, which has been applied to metal tube rotameter now.Firstly, through the rotameters'measurement principle and magnetoresistance sensors'working principle being studied on, the implement methods of the two kinds of techniques, which is using pure solid sensors and semisolid sensors to measuring the floating element's position of metal tube rotameter, is put forwarded in this paper. And their performance and feature is studied and analyzed respectively.Secondly, the design of semisolid sensors'hardware system is introduced in detail, which comprises power supply with 24V voltage, battery, and 24V voltage according with HART protocol.Thirdly, for the semisolid sensors, a software system based onμC/OS-II is carried out on MSP430, which increases its performance of the extensibility and migration. Intelligentized characteristic is realized on the flowmeter, and it can be used to measure flow rate of different mediums, different density and different work situation through the keys to set parameters. The instantaneous flow rate and cumulative flow can be displayed on the liquid crystal's screen real-time.Finally, many experiments, including temperature experiments and flow experiments, are carried out with the metal tube rotameters whose floating element's position is measured by the semisolid sensors. Experimental results indicate that the measuring precision ratio of the metal tube rotameter adopted this technology is 1.5%, and the maximum temperature drift is only -0.143%/10°C.