Use of the impedance method for ICNIRP-related compliance testing of electronic article surveillance devices

Abstract

Electronic article surveillance (EAS) systems based on the use of alternating magnetic fields at frequencies up to 10-20 MHz are being rapidly introduced into society to prevent unauthorized removal of items from stores, libraries, and hospitals. The EAS systems may take the form of one or two-sided panels of current-carrying loops or pillars at or near the exit door, and loops hidden in the ceiling and/or the mat on the floor. Another manifestation is the magnetic tag deactivation systems that are mounted as checkout counter top devices. The net result is that an individual passing through or standing close to these devices is exposed to nonuniform vector magnetic fields emanating from these EAS systems. Limits of induced current densities in the human body have been prescribed in the IEEE and ICINIRP standards that may not be exceeded for exposure of the general public or for occupational situations. Computational methods using heterogeneous anatomically-based models of the human body are acceptable to show compliance of new EAS devices. For the present paper, we have used the widely accepted 3-D impedance method to calculate the currents induced in the human body for some representative EAS devices. Since the purpose of the paper is to illustrate the approach and the kind of results that one may expect, the geometrical configurations, the ampere turns and the frequencies have been altered from those used in commercial devices.