A Passive Field Conversion–Amplification Scheme: Demonstrated by Integrating a Magnetic Cantilever With a TMR for Current Monitoring

A passive field conversion–amplification scheme is proposed and demonstrated for the first time by integrating a magnetic cantilever with a tunnel magnetoresistance (TMR) for current monitoring. In the scheme, a magnetic structure with a strong field is driven and vibrated by the interaction with a weak field. The passive movement of the magnetic structure physically results in a movement of a strong field. The weak field is, thus, converted by the movement and further passively amplified into a strong one. The degree of the amplification is determined by the structure geometry, the position of the magnetic structure, as well as the weak field. In this article, a TMR cantilever current sensor, mainly composed of two units, is developed to demonstrate the proposed scheme. One is a cantilever with a permanent magnet fixed at its free end as a sensing unit and the other is the TMR as a detecting unit. The experimental measurements demonstrate that a higher detection sensitivity can be achieved with the proposed scheme, compared to that with only TMR detection. The gain of the sensitivity reaches more than an order of magnitude. If an energy harvesting unit is further integrated into the proposed current sensor, a self-powered sensing node can be accomplished for potential wireless sensor network applications.