Research And Design Of Micro-Electrical Impedance Tomography System Based On LabVIEW

Electrical impedance tomography is a new type of imaging technology that realizes target imaging through the distribution of resistivity.Different types of biological tissues have different impedances,or the electrical impedance of biological tissues changes in some special cases.The tissue is injected with excitation current,the voltage difference signal on the sensing electrode is collected,and the corresponding algorithm is used to reconstruct the internal impedance distribution of the tissue.Finally,the characteristic information of the tissue is obtained to achieve the purpose of non-damage detection.In this paper,we design an imaging system of electrical impedance tomography reconstruction for micro-objects which can be referred to as Micro-Electrical Impedance Tomography(MEIT),and initially build multiple functional modules required by the system.The main tasks are as follows:(1)The hardware part includes of 16-channel miniature electrode physical model,three-op amp current source,multi-way switch with optoelectronic couplers,pre-isolation circuit,high-precision instrumentation amplifier,secondary amplifier circuit Etc.Among them,the micro physical model of 16-channel consists of a 3D printed container and micro-electrodes which are made of the through holes of a PCB board.Circuits in the board are used instead of wires to reduce signal interference.Three op amp voltage-to-current circuit improves the stability of the current source and reduces the cost of the circuit.In order to prevent current crosstalk from affecting weak voltage data collection,there are optoelectronic couplers between the multiplexer and the data acquisition card.(2)The software part which is written by Lab VIEW,consists of the acquisition and control module and the imaging algorithm design module.The acquisition and control module controls the generation of the excitation voltage signal,the acquisition of the voltage signal,the switching of the multiple switching sequence and the processing of the data.In the image reconstruction module,it studies the regularization algorithm based on spectrum graph wavelet,and realizes the electrical impedance tomography by Lab VIEW.(3)The test section completes the performance test of the system and each module.Including the test of the output impedance and stability of the excitation current source,the function test of the signal conditioning circuit and the channel consistency test.Finally,the system is used for experiment tests,which collects voltage data from the measured object of different types,different shapes,and different positions,and realizes the electrical impedance tomography with the regularization algorithm of the spectrum graph wavelet.Experimental results show that the electrical impedance tomography system has a certain imaging effect on miniature objects,and can effectively achieve the positioning and detection of the measured object.