Highly sensitive anisotropic magnetoresistance magnetometer for Eddy-current nondestructive evaluation

Abstract

Using a commercially available anisotropic magnetoresistance (AMR) sensor of HMC1001, we developed a sensitive magnetometer. It could operate in amplifier mode or feedback mode. The magnetic field sensitivity of the AMR sensor was about 3.2 mV/V G. When the AMR sensor was biased by a voltage of 24 V, the magnetic field resolutions of the AMR magnetometer were about 12 pT/square root(Hz) at 1 kHz and 20 pT/square root(Hz) at 100 Hz. We used the AMR magnetometer for Eddy-current nondestructive evaluation in unshielded environment.

High sensitive magnetic sensor with amorphous wire

“…There are many kinds of magnetic sensors: inductive coil [1], Fluxgate magnetometer [2], Giant magneto resistive (GMR) sensor [3], anisotropic magneto resistive (AMR) sensor [4], magneto-impedance (MI) sensor [5,6], superconducting quantum interference device (SQUID) [7]. Inductive coil sensor cannot measure DC magnetic field and its sensitivity is worse at low frequency.…”

AMR Sensor and its Application on Nondestructive Evaluation

“…Figure 4 shows the block diagram of the circuit. The driving circuit could operate in amplifier mode or feedback mode [13]. We used a voltage source to bias the AMR sensor.…”

“…The results show that AMR sensor had the lowest magnetic field noise spectrum density with the order of 100 pT/root(Hz) in the frequency range from 1 Hz to 1 kHz. And we also achieved much better performances by optimizing the driving circuit of the AMR sensor [13], so we chose AMR sensor to construct our ECT NDE systems.…”

An anisotropic magneto resistive sensor with set/reset field

“…7 This problem becomes severe when using big bias voltage to increase the sensitivity of AMR sensor. 8 Besides producing a noise signal, the thermal effect also causes the change of the sensitivity of the AMR sensor, which increases the noises in other applications, such as eddy-current testing using AMR sensor. Therefore, it is necessary to develop a method to reduce the influence of temperature drifting and the heat transfer effect of AMR sensor.…”

“…8 Due to the power consumption, the surface temperature of the AMR sensor was about 60 • C for the 20 V bias voltage. Noise signal was produced due to the heat transfer effect for the magnetic particle detection.…”