Data Acquisition System For Electrical Capacitance Tomography Based Lab VIEW

Electrical Capacitance Tomography (ECT) is a process tomography, with simple structure, low cost, non-invasive, has wide application scope. This paper briefly introduces electrical capacitance tomography, summarizes the research of ECT at home and abroad, describes the whole scheme of ECT, compares several common capacitance measuring circuits and capacitance compensation methods, analysis the data acquisition system for ECT based on signal measurement channel and multi measurement channels, determines ECT system based on double measurement channels, analysis the effect of phase angle cased by capacitance measuring circuit for capacitance measurement circuit sensitivity, sets up reasonable circuit parameters, makes the effects minimum, analysis the switch arrangement and the effect of coupling capacitance and the solution, and focuses on the hardware and software of data acquisition system for ECT based on virtual instrument.Its hardware system was composed of signal generator, MUX, ac-based capacitance measuring circuits, signal conditioning circuits, data acquisition card based PCI bus, and a computer with LabVIEW. By using virtual instrument technology and LabVIEW platform, realizes the whole process of excitation signal generate, the capacitance measurement, and data storage. The system provides friendly communication panels for users, at the time of system processing, users can synchronously observe the wave of two channel measuring signal, the real-time data, and the output of every measuring channel.The system is tested on the condition of lab, including linearity experiment, coupling capacitance compensation experiments and static capacitance calibration experiment. The experiment results indicate that the system has good linear between the voltage and capacitance, can measure and store the capacitance between any two electrodes, and after compensated capacitance output amplitude stability, obviously superior to compensate the capacitance before, verifies the software compensation method is effective.