Induction Magnetometer with a Metal Shielded Pickup Coil for MHz Range Operation

Abstract

This paper presents an induction magnetometer with a metal shielded pickup coil for MHz range operation. The validity of two simple equivalent circuit models for voltage detection and current detection is also confirmed by experimental results. From the measured frequency response for a calibrated magnetic field of 10 nT, we successfully demonstrate the ability of the magnetometer. The experimental results reveal the quantitative data of the equivalent resistance and inductance. When the resistance of the pickup coil is quite low, the equivalent resistance can be regarded as the resistance of the BNC connector (50 Ω). With the equivalent resistance, the absolute error of the output voltage between measurement and estimation is less than ±1 dBμV between 0.3 MHz and 2 MHz. In contrast, it is found that the existence of the metal shielded layer affects the estimated equivalent inductance. If the pickup coil has no metal shielded layer, the estimated value of the equivalent inductance is 56.3 times the inductance of the pickup coil. This value is verified by the estimated and measured results. However, this phenomenon is not found if the pickup coil has the metal shielded layer.