| Electrical Resistance Tomography (ERT) is a novel cross section measurement technology developed in recent years. It can achieve the visualization measurement of multi-phase media component parameter in the closed pipe and process vessel inside. And it has the virtue of non-intrusive, non-radiation and on-line visual monitoring. And it is now in a great prospective in two-phase flow. At present, there are still some difficulties in its implementation in the industrial field because the real-time performance of ERT can't satisfy the speed requirement for on-line measurement. This dissertation begins with the analysis of real-time performance of the ERT system and presents a new ERT system with parallel data acquisition strategy. The main researches are as follow:1. The real-time performance of the parallel data acquisition system for ERT is analyzed. The low-pass filter (LPF), which costs the most time of the data acquisition process, is simulated. The response times of LPF and data acquisition speed are investigated when the band of the signal frequency is from 60 KHz to 200 KHz. When the frequency is 60 KHz, the data acquisition speed can achieve at 742 frames per second; when the frequency is 200 KHz, the data acquisition speed can achieve at 1366 frames per second.2. The parallel data acquisition system for ERT is presented. Basing on the analysis of real-time performance, an I/O card and two data acquisition cards which are based on PCI bus are used in this system. And system is module structured with the user-defined bus This ERT system consist of the exciting signal source module, the sensor and selection logic module, DAS module, signal pretreatment module, logic and time module and the baseboard. The DAS module and signal pretreatment module consist of 16 groups of amplifiers, 16 groups of demodulators and filters and 16 groups of AD.3. The modules are individually tested and the distribution of the sensing field is measured preliminarily with complete and valid signals. |
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