A magnetic induction measurement system for adult vital sign monitoring: Evaluation of capacitive and inductive effects

Abstract

Magnetic induction (MI) measurement technique could provide an unobtrusive contactless method for continuous monitoring of vital signs such as breathing and cardiac activity in bed. In this paper, we present a magnetic induction system to evaluate the feasibility of monitoring heart and lung activity and the preliminary measurement results. The excitation and detection coils are designed to be implemented in a single printed circuit board, allowing the use of the system in a bed with coils under the mattress. The electronic system is based on a 16 bit arbitrary waveform generator (PXI-5422, National instrument) operating at a sample rate of 200 MS/s for the excitation signal and the detected amplified signal is then, sampled at 100 MS/s by a 14 bit digitizer (PXI-5122, National Instruments). The preliminary results at 10 MHz show the ability of the system to detect solutions with different conductivities. However the capacitive effect is in the same order of magnitude as the inductive effect due to eddy currents. Safety of the system has been evaluated to be in accordance with the standards of human exposure to the magnetic fields.