Noise measurement and system calibration on magnetoresistive sensors

Abstract

Purpose The noise measurement on magnetoresistive (MR) sensors is generally conducted by techniques including single-channel data sampling and fast Fourier transform (FFT) analysis as well as two-channel cross-correlation. The single-channel method is easy to implement and is widely used in the noise measurement on MR sensors, whereas the two-channel method can only eliminate part of the system noise. This study aims to address two key issues affecting measurement accuracy: calibration of the measurement system and the elimination of system noise. Design/methodology/approach The system is calibrated by using a low-noise metal film resistor in that the system noise is eliminated through power spectrum subtraction. Noise measurement and analysis are conducted for both thermal noise and detectivity of magnetic tunnel junction (MTJ) sensor. Findings The thermal noise measurement error is less than 2%. The detectivity of the MTJ sensor reaches 27 pT/Hz1/2 at 2 kHz. Originality/value This study provides a more practical solution for noise measurement and system calibration on MR sensors with a bias voltage and magnetic field.

Dual-range TMR current sensor based on magnetic shunt/aggregation effects utilizing single magnetic ring structure

“…The resolution of the current sensors is directly related to the sensor noise. Our previous research indicates that compared to the open-loop configuration, the closed-loop sensors show slightly higher noise levels [21,22]. Therefore, in our subsequent study, we will systematically analyze the noise of dual-range closed-loop current sensors and optimize the feedback circuit design accordingly.…”

Equivalent Noise Analysis and Modeling for a Magnetic Tunnel Junction Magnetometer with In Situ Magnetic Feedback

“…As shown in Figure 7, the noise measurement system is built using a high-precision dynamic signal acquisition (DSA) card and a low-noise preamplifier (LNP) [26][27][28]. The magnetometer, Helmholtz coils, and LNP are placed in a magnetic shielding chamber for shielding environmental magnetic fields.…”

“…The noise measurement system is calibrated with a commercial metal film resistor whose resistance is 4.73 kΩ, and the precision of the system is about 2% [26].…”

“…The noise power at the output of the MTJ sensor is equal to the noise in one bridge arm when the four arms of the Wheatstone bridge have equivalent noise sources [1,20]. The noise of the MTJ sensor consists of thermal-electronic noise, shot noise, thermal-magnetic noise, electronic 1/f noise, and magnetic 1/f noise [1,2,17,20,21,26].…”

“…Since the thermal-shot noise, thermal-magnetic noise, electronic 1/f noise, and magnetic 1/f noise are incoherent, the total noise power is the superposition of all the uncorrelated noise sources mentioned above [1,2,20,21,26]. The noise power spectral density (unit of V 2 /Hz) of the MTJ sensor is described as…”