Low frequency noise of anisotropic magnetoresistors in DC and AC-excited metal detectors

7th Sensors & their Applications

Vyhnanek, J.^1 ; Janosek, M.^1 ; Ripka, P.^1

Czech Technical University in Prague, Technicka 2, 166 27 Prague, Czech Republic^1

关键词: Combined processing;    Giant magnetoresistive;    High spatial resolution;    Low-Frequency Noise;    Low-frequency response;    Low-noise measurements;    Non destructive testing;    Processing electronics;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/450/1/012031/pdf
DOI  :  10.1088/1742-6596/450/1/012031

来源: IOP

【 摘 要 】

Magnetoresistors can replace induction sensors in applications like non-destructive testing and metal detection, where high spatial resolution or low frequency response is required. Using an AC excitation field the magnetic response of eddy currents is detected. Although giant magnetoresistive (GMR) sensors have higher measuring range and sensitivity compared to anisotropic magnetoresistors (AMR), they show also higher hysteresis and noise especially at low frequencies. Therefore AMR sensors are chosen to be evaluated in low noise measurements with combined processing of DC and AC excitation field with respect to the arrangement of processing electronics. Circuit with a commercial AMR sensor HMC1001 and AD8429 preamplifier using flipping technique exhibited 1-Hz noise as low as 125 pT/. Without flipping, the 1-Hz noise increased to 246 pT/.