Current driven magnetic permeability interference sensor using NiFe/Cu composite wire with a signal pick-up LC circuit

A novel micro magnetic sensor called the Current Driven Magnetic Permeability Interference (CDMPI) sensor has been developed and the key parameters of the sensor have been studied. The sensor consists of a sensing element in a form of composite wire of a 20 μm copper core electrodeposited with a thin layer of soft magnetic material (Ni ₈₀Fe ₂₀), an ac power source driving the permeability of the magnetic coating layer of the sensing element into a dynamic state, and a signal pickup LC circuit formed by a pickup coil and an capacitor. Experimental studies on the CDMPI sensor have been carried out to investigate the key parameteres in relation to the sensor sensitivity and resolution. The results showed that for high sensitivity and resolution, the frequency and magnitude of the ac driving current through the sensing element each has an optimum value, the resonance frequency of the signal pickup LC circuit should be equal to or twice as the driving frequency on the sensing element, and the anisotropy of the magnetic coating layer of the sensing wire element should be longitudinal.