Automated system for noise-measurements on low-ohmic samples and magnetic sensors

Jonker, R.J.W.; Briaire, J.; Vandamme, L.K.J.

doi:10.1109/19.772210

Cited by 8 publications

(4 citation statements)

References 13 publications

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“…The two-channel cross-correlation technique is commonly employed to effectively reduce the noise floor of the measurement system. 2 AMR ͑bridge͒ 1.0 k⍀ No sor will be correlated on the two channels, while that from the two amplifiers and any spurious pickup on the cables will not be correlated. In order to minimize power supply noise the preamps are powered by lead-acid batteries.…”

Section: Measurementmentioning

confidence: 96%

Low-frequency noise measurements on commercial magnetoresistive magnetic field sensors

Stutzke

Russek

Pappas

et al. 2005

Journal of Applied Physics

205

111

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Low-frequency noise was measured in the frequency range from 0.1Hzto10kHz on a variety of commercially available magnetic sensors. The types of sensors investigated include anisotropic magnetoresistance (AMR), giant magnetoresistance (GMR), and tunnel magnetoresistance (TMR) effect devices. The 1∕f noise components of electronic and magnetic origin are identified by measuring sensor noise and sensitivity at various applied magnetic fields. Commercial magnetometers typically consist of four elements in a Wheatstone bridge configuration and are biased with either a constant voltage or current. Voltage fluctuations at the sensor output are amplified by a pair of battery powered low-noise preamplifiers and input to a spectrum analyzer. A two-channel cross-correlation technique is used when the performance of a single preamplifier is not sufficient. For the AMR and GMR sensors investigated, both electronic and magnetic components contribute to the overall sensor noise. Maximum noise occurs at the bias field which gives maximum sensitivity. The noise of TMR based sensors is primarily due to resistance fluctuations in the tunnel barrier, having little to no field dependence. The best low-field detectivity of the sensors that have been measured is on the order of 100pT∕Hz0.5 at 1Hz.

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Section: Measurementmentioning

confidence: 96%

Low-frequency noise measurements on commercial magnetoresistive magnetic field sensors

Stutzke

Russek

Pappas

et al. 2005

Journal of Applied Physics

205

111

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“…Programmability can be obtained by employing relays for switching a network of resistances in such a way as to obtain different values of series resistances and, hence, different currents. 3 In other cases, a programmable solid state voltage source with a sufficiently large series resistance can be used to set the bias current through a sample with high resolution. 4 While effective in some cases, the abovementioned approaches can seldom provide the very high internal impedance that would be desirable for a current source.…”

Section: Introductionmentioning

confidence: 99%

Programmable, very low noise current source

Scandurra

Cannatà

Giusi

et al. 2014

Review of Scientific Instruments

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We propose a new approach for the realization of very low noise programmable current sources mainly intended for application in the field of low frequency noise measurements. The design is based on a low noise Junction Field Effect Transistor (JFET) acting as a high impedance current source and programmability is obtained by resorting to a low noise, programmable floating voltage source that allows to set the sourced current at the desired value. The floating voltage source is obtained by exploiting the properties of a standard photovoltaic MOSFET driver. Proper filtering and a control network employing super-capacitors allow to reduce the low frequency output noise to that due to the low noise JFET down to frequencies as low as 100 mHz while allowing, at the same time, to set the desired current by means of a standard DA converter with an accuracy better than 1%. A prototype of the system capable of supplying currents from a few hundreds of μA up to a few mA demonstrates the effectiveness of the approach we propose. When delivering a DC current of about 2 mA, the power spectral density of the current fluctuations at the output is found to be less than 25 pA/√Hz at 100 mHz and less than 6 pA/√Hz for f > 1 Hz, resulting in an RMS noise in the bandwidth from 0.1 to 10 Hz of less than 14 pA.

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“…There are two noise measurement techniques for MR sensors. One is single-channel data sampling and fast Fourier transform (FFT), and the other is two-channel cross-correlation (Davies et al , 2021; Roldán et al , 2014; Jonker et al , 1999; Stutzke et al , 2005; Yuan et al , 2016; Cao et al , 2016). Dual preamplifiers measure the noise of the same MR sensor, and uncorrelated noise can be eliminated through cross-correlation.…”

Section: Introductionmentioning

confidence: 99%

Noise measurement and system calibration on magnetoresistive sensors

Dou

Bai

Zhu

et al. 2023

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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.

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Automated system for noise-measurements on low-ohmic samples and magnetic sensors

Cited by 8 publications

References 13 publications

Low-frequency noise measurements on commercial magnetoresistive magnetic field sensors

Low-frequency noise measurements on commercial magnetoresistive magnetic field sensors

Programmable, very low noise current source

Noise measurement and system calibration on magnetoresistive sensors

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