Validation of a measurement method for magnetic shielding effectiveness of a wire mesh enclosure with comparison to an analytical model

Abstract. This paper deals with the validation of a measurement method for determining the magnetic shielding effectiveness of a wire mesh enclosure in the frequency range from 10 kHz to 150 kHz. The comparison with an analytical model (parallel-plate-shield, see Kaden, 1959) for magnetic shielding effectiveness of wire mesh is also part of this contribution. To measure the shielding effectiveness of an enclosure in general, two steps are necessary:

1. Reference measurement of the incident electro-magnetic field.
2. Measurement of the incident electro-magnetic field in the enclosure by same conditions.

This method presented in the contribution uses a Helmholtz coil as magnetic field source, controlled by a signal generator and an amplifier in voltage mode. At first, a field meter was used to measure the frequency dependent magnetic field in the center of the Helmholtz coil. The magnetic field strength was also analytically calculated and compared to the measurement results. The next step was to measure the induction voltage caused by the magnetic field with a magnetic field probe, which was later used for the measurements of the shielding effectiveness either. A signal amplifier was needed to raise the signal-to-noise-ratio (SNR). The gain of the signal amplifier was also determined and measured. Two positions of the enclosure in the Helmholtz coil were considered, horizontal and vertical. The vertical position of the enclosure approaches the analytical model of Kaden (1959) closely and the results show a good match with the analytical model.