Konferenzbeiträge

A contact-less, interference-free approach for the detection of cardiac mechanics and respiration by means of multi-channel ultra-wideband (UWB) radar was developed [2], suitable to deliver trigger signals for cardiac MR imaging. Compared to previous systems we increased the number of antennas to four transmitters and eight receiver antennas. This allows measurements of up to 32 channels and makes UWB motion detection less sensitive to the particular positioning of the antennas relative to the heart.

We report an investigation of the motion of a freefalling permanent magnet in an electrically conducting pipe containing an idealized defect. This problem represents a highly simplified yet enlightening version of a method called Lorentz force eddy current testing which is a modification of the traditional eddy current testing technique. Our investigation is a combination of analytical theory, numerical simulation and experimental validation. The analytical theory allows a rigorous prediction about the relation between the size of the defect and the change in falling time which represents the central result of the present work. The numerical simulation allows to overcome limitations inherent in the analytical theory. We test our predictions by performing a series of experiments. We conclude that our theory properly captures the essence of Lorentz force eddy current testing although a refinement of the experiment is necessary to reduce the discrepancy to the predictions. In spite of its apparent simplicity the present system can serve as a prototype and benchmark for future research on Lorentz force eddy current testing.