Frequency domain test scheme of a current source for nuclear magnetic resonance

Abstract

Nuclear magnetic resonance techniques in magnetic metrology applications require the generation of a highly homogeneous field. This is achieved by exciting a magnet with a high-stability variable current source or feeder. One way to improve the source's reliability is by employing periodic field testing strategies. This work proposes a structural-type test for a feeder based on a three-phase converter with Cuk topology that employs low-complexity measurements. In test mode, the open-loop circuit under test is exercised with a stimulus that causes a step variation in the output current. The current signal is analyzed using a fast Fourier transform. It is assumed that a fault will cause a variation in the magnitude of selected spectrum components, making it observable. The test performance is evaluated through a fault injection and simulation procedure on the Matlab Simscape platform, employing models of single catastrophic faults. The work includes an analysis of the detection capacity of the method under conditions of variability in the power supply of the source. The fault injection and simulation campaign results show that the method's efficiency is very good, with only a single undetected fault.