Parameter Measurement for Conducting Liquid Based on Electromagnetic Technique
|Course||Control Science and Engineering|
|Keywords||Electromagnetic detection High frequency Level measurement Phase holdup measurement|
The research in this thesis attributes to electromagnetic detection technology. Thepurpose of this study is to measure the real-time parameters of low conductivitymaterial based on high frequency electromagnetic excitation and novel design ofelectromagnetic sensor.Electromagnetic detection technology is defined as the physical parametersmeasurement technology using the electromagnetic principle and electromagneticphenomena. Electromagnetic detection technology is a kind of nondestructive testingtechnology with several advantages, such as fast inspection speed, high sensitivity,good reliability and being non-contact and noninvasive. Electromagnetic detectiontechnology usually takes electromagnetic induction as the basic principle, useselectromagnetic coil as sensors and seek conductivity and permeability as the maindetection parameters.Since2007, the Electromagnetic Detection Technology Group of TianjinUniversity has completed lots of studies, such as low-frequency analogelectromagnetic tomography system, high frequency digital electromagnetictomography system, parameters measurement for metal workpieces based onelectromagnetic detection and so on. On the basis of these above researches, thisthesis achieved parameters measurement for low conductivity materials by highfrequency electromagnetic excitation system, which has considerable significance inelectromagnetic detection.The main novelties of this thesis are embodied in4points as follows:1、 High-frequency electromagnetic excitation system was developed. In orderto achieve parameters measurement for low conductivity material, it isnecessary to increase excitation frequency of the electromagnetic detectionsystem. Front-end circuit and multistage amplifier circuit were designed toovercome the problems of signal transmission, noise interference and signalprocess.2、 Sensitivity calculation and sensor optimization design. The sensitivityformula of electromagnetic detection system was deduced and the sensitivitycalculation method was proposed. The sensor sensitivity evaluation indexes were defined and sensor structure of electromagnetic excitation system wasoptimized based on these indexes.3、 Phase holdup measurement system based on electromagnetic spiral sensorswas developed. A novel sensor with spiral structure was designed and thesensitivity matrixes of4kinds of sensors were calculated by2methodscalled field value extraction method and perturbation method. Theoptimization of electromagnetic sensor’s angle was completed based onsensor sensitivity evaluation indexes and the phase holdup measurementexperiment based on electromagnetic spiral sensors was developed.4、 Conductive liquid level measurement system based on high frequencyelectromagnetic system was developed. The optimal electromagnetic sensorconfiguration in different liquid level measurement occasions wasdetermined by sensitivity calculation. The conductive liquid levelmeasurement experiment was carried out and the error analysis wasconducted. The measurement procedures and relative guidelines about themeasurement based on high frequency electromagnetic excitation werepresented.