Research Of The Capacitive Coupling Electromagnetic Flow Measurement Technology Based On Helmholtz Coils

The flow measurement technology is a very important technological means, which is widely used in lots of fields such as agriculture, industry, aerospace and so on. As one of the most widely used flow measurement technology, electromagnetic flow measurement technology is based on Faraday’s law of electromagnetic induction, this kind of measurement technology can apply in measuring the liquid that has good electrical conductivity, it has high reliability, strong anti-erosion performance and some other advantages. The capacitive coupling electromagnetic flow measurement technology not only has the advantages which the traditional electromagnetic flow measurement technology has already had, but also has its own special advantages. For example, it has wide measurement range, its measurement precision is high, its electrode needn’t direct contact the liquid etc. So this kind of flow measurement technology has wider applied range than others, it also meaningful to do research on it.In this research, we designed a set of flow measuring device which is based on the capacitive coupling electromagnetic flow measurement technology, this device is composed of two parts, one is excitation equipment and the other is signal detector. The excitation equipment consists Helmholtz coils and excitation signal producing circuit, the details of coils and circuit are all need to be reasonable set, in order to make the Helmholtz coils generating proper magnetic field for flow measurement. The signal detector contains measuring tube, capacitive coupling electrode and signal detection circuit. As sensitive element, measuring tube and capacitive coupling electrode should be designed in proper material and construction. The signal detection circuit is used to convert the signal from electric current to voltage, differential amplification and other signal conditioning, as a result the flow information can be fetched.Firstly, this paper discusses the development status and merits and demerits of some kinds of flow measurement technology, capacitive coupling electromagnetic flow measurement technology is discussed as the main part. Then, on the basis of reading a big amount of reference home and abroad, analyze the principle of the capacitive coupling electromagnetic flow measurement technology in details; and then, the designing scheme of the flow measuring device is discussed in two parts: excitation equipment and the signal detector, a computer simulation is also be done about the magnetic field generating by the Helmholtz coils, and discussed a related algorithm on extracting signal from noise jamming; In the end, we set up an experimental platform, which is a water circulation system, and do experiments on the flow measuring device to get some experimental data. Through the experiment, the applicable of the flow measuring device can be verified.