Magnetic Induction Tomography is a contactless imaging technique which uses a coil array to induce eddy currents to a conductive object and detects the secondary magnetic field containing the conductivity information. Magnetic Induction Tomography instrumentation for low conductivity applications (σ<30 S/m) is very demanding due to the low amplitude signals. Depending on the application a high data acquisition rate might be required.The aim of this study was to investigate and develop practical and inexpensive high speed Magnetic Induction Tomography instrumentation to provide a solution to low conductivity applications requiring high data acquisition rate. Specifically the multiphase flow in oil pipes and the detection of the cardiac activity and the lung activity were targeted.A thorough investigation for the specifications, the design and the development of the required MIT instrumentation was performed. Two low cost MIT systems operating at 10 MHz based on the zero crossing phase measurement technique were developed and implemented.The eight channel Cardiff Mk2c aimed at the multiphase flow in oil pipes. The Cardiff Mk2c achieved a frame rate of 12.5 frames per second making it the fastest 10 MHz multichannel MIT system until this thesis was submitted. Its precision was down to 15 millidegrees. The Cardiff Mk2c detected the flow of 250 ml volume of 3 S/m saline through an inclined water pipe. The detected signal had a duration of 200 ms and the system's observed maximum peak SNR was 38.75 dB.The single channel Cardiff Mk2d aimed at the detection of the cardiac activity and the lung activity making it the first zero crossing system used for these applications. The Cardiff Mk2d used a recording rate of 20 Hz and achieved a phase precision down to 4 millidegrees. Measurement with four human volunteers were taken in which the Cardiff Mk2d detected successfully the heart rate and the respiration rate concurrently.
|Date of Award
|Ralf Patz (Supervisor) & Stuart Watson (Supervisor)