Lock-in amplifiers for AMR sensors

Díaz-Michelena, Marina; Cobos, P.; Aroca, C.

doi:10.1016/j.sna.2014.11.005

Cited by 20 publications

(14 citation statements)

References 14 publications

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“…The simultaneous measurement of the temperature and the magnetic field during the prospections diminishes this problem, which can be neglected in areas with magnetic anomalies > 100 nT, but the error can be significant (1 %) in low contrast anomalies (in the range of 1 nT), also due to the resolution of the MOURA instrument. Other ways to compensate the temperature effects could improve these errors (Díaz-Michelena et al, 2015b). For static measurements the simultaneous temperature measurement corrects very well the magnetic field data (Díaz-Michelena et al, 2015a).…”

Section: Instrument Performancementioning

confidence: 99%

Mars MOURA magnetometer demonstration for high-resolution mapping on terrestrial analogues

Díaz-Michelena

Kilian

Sanz

et al. 2016

Geosci. Instrum. Method. Data Syst.

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Abstract. Satellite-based magnetic measurements of Mars indicate complex and very strong magnetic anomalies, which led to an intensive and long-lasting discussion about their possible origin. To make some progress in the investigation of the origin of these anomalies the MOURA vector magnetometer was developed for in situ measurements on Mars. In this work we propose the utilisation of such an instrument for future planetary on-ground surveys. The proof of its suitability is seen through testing it on various terrestrial analogues characterised by the distinct magnetic anomalies of their basement rocks: (1) a magnetite body of EL Laco (up to +110 000 nT) and its transition to surrounding andesites (< +2000 nT) in the northern Andes of Chile showing the highest local magnetic anomalies. The magnetite-bearing ore body has highly variable local anomalies due to its complex formation history where a significant dispersion in palaeoorientations has been previously reported, while our vector data show relatively uniform and probably induced declinations. (2) A basaltic spatter cone of the Pali Aike volcanic field, in southern Chile, was characterised by very strong magnetic anomalies along the crater rim (up to +12 000 nT), controlled by the amount of single domain magnetites in the ground mass of the basalts. Due to their strong remanent signature, palaeo-declinations of the lavas and reorientations of collapsed blocks could be constrained by the vector data. (3) The Monturaqui meteorite crater (350 m diameter), in northern Chile, shows significant variations of its anomalies (from −2000 to > +6000 nT) in restricted areas of several square metres along its crater rim related to unexposed iron-bearing fragments of the impactor while its granitic and ignimbritic target rocks exhibit only very weak anomalies. (4) An area with several amphibolitic dykes, which cross-cut a Cretaceous granitoid in the southernmost Andes, where a decimetre-scale mapping was performed. In this case, pyrrhotite is the only magnetic carrier. It was formed during hydrothermal processes within the dykes. Very low (+40 to +120 nT) positive magnetic anomalies clearly depict the amount of 1-4 vol % pyrrhotite in these dykes, which is important as a mineralogical indicator as well as to detect associated gold and copper enrichment.

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Section: Instrument Performancementioning

confidence: 99%

Mars MOURA magnetometer demonstration for high-resolution mapping on terrestrial analogues

Díaz-Michelena

Kilian

Sanz

et al. 2016

Geosci. Instrum. Method. Data Syst.

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“…Advances in magnetic sensor technology now permit sufficient sensitivity to low-amplitude (nanotesla) fields using inexpensive sensors with phase-sensitive detection; 6,20,25 therefore, there is interest in developing this NDE method for monitoring of CUI using an array of permanently installed sensors. Anisotropic magnetoresistive (AMR) sensors are used as they offer excellent sensitivity to low fields; however, thermal drifts can affect their sensitivity by ∼0.25–0.27%/°C due to the variation of resistivity and the magnetoresistive effect with temperature, in addition to a temperature-dependent bridge offset.…”

Section: Introductionmentioning

confidence: 99%

“…Anisotropic magnetoresistive (AMR) sensors are used as they offer excellent sensitivity to low fields; however, thermal drifts can affect their sensitivity by ∼0.25–0.27%/°C due to the variation of resistivity and the magnetoresistive effect with temperature, in addition to a temperature-dependent bridge offset. 25 To further develop the technique into a deployable SHM solution requires an understanding of the limitations of the sensitivity in practical SHM. This conventionally requires many controlled tests of structures with physically growing defects, which can be time-consuming and expensive.…”

Section: Introductionmentioning

confidence: 99%

Permanently installed corrosion monitoring using magnetic measurement of current deflection

Jarvis

Cawley

Nagy

2017

Structural Health Monitoring

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The detection of corrosion on insulated and/or coated pipes remains a challenge. A non-destructive evaluation method has been proposed where a low-frequency AC current is directly injected into the pipe at distant locations, and perturbations in the magnetic field induced by current deflection around defects are measured. Structural health monitoring is made possible by detecting changes in the magnetic field due to defect growth using a permanently installed array of sensitive and inexpensive magnetic sensors. The performance of current deflection structural health monitoring is evaluated using a flexible and efficient framework. Individual sensor performance was first predicted using receiver operating characteristics obtained by evaluating the stability of the magnetic field signal measured outside of a section of coated undamaged riser pipe in an environmental chamber over repeated temperature cycles. A finite element model was then used to predict the magnetic perturbation due to defect growth which allowed the potential array configurations for structural health monitoring to be explored. Results suggest that 90% probability of detection and 0.1% probability of false alarm for [Formula: see text] (wall thickness) diameter, 30% of T depth defects are possible outside of 25- to 50-mm-thick pipe coatings/insulation using 10–50 sensors per metre of pipe and 5–10 A of injected current. The structural health monitoring procedure was then demonstrated experimentally, an electrochemically grown defect being successfully monitored; this experiment also served to validate the three-dimensional finite element model. A very good agreement between the predicted and measured changes in the magnetic field due to the current deflection around the growing defect was obtained.

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“…A lock-in amplifier is an extremely effective system for detecting a weak signal with a low signal-to-noise ratio [1,2,3,4]. It has been widely used in various kinds of instrument, as well in logging tools, such as nuclear magnetic resonance (NMR) logging tools, acoustic logging tools and resistivity logging tools [5,6,7,8].…”

Section: Introductionmentioning

confidence: 99%

A Digital Lock-In Amplifier for Use at Temperatures of up to 200 °C

Cheng

et al. 2016

Sensors

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Weak voltage signals cannot be reliably measured using currently available logging tools when these tools are subject to high-temperature (up to 200 °C) environments for prolonged periods. In this paper, we present a digital lock-in amplifier (DLIA) capable of operating at temperatures of up to 200 °C. The DLIA contains a low-noise instrument amplifier and signal acquisition and the corresponding signal processing electronics. The high-temperature stability of the DLIA is achieved by designing system-in-package (SiP) and multi-chip module (MCM) components with low thermal resistances. An effective look-up-table (LUT) method was developed for the lock-in amplifier algorithm, to decrease the complexity of the calculations and generate less heat than the traditional way. The performance of the design was tested by determining the linearity, gain, Q value, and frequency characteristic of the DLIA between 25 and 200 °C. The maximal nonlinear error in the linearity of the DLIA working at 200 °C was about 1.736% when the equivalent input was a sine wave signal with an amplitude of between 94.8 and 1896.0 nV and a frequency of 800 kHz. The tests showed that the DLIA proposed could work effectively in high-temperature environments up to 200 °C.

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Lock-in amplifiers for AMR sensors

Cited by 20 publications

References 14 publications

Mars MOURA magnetometer demonstration for high-resolution mapping on terrestrial analogues

Mars MOURA magnetometer demonstration for high-resolution mapping on terrestrial analogues

Permanently installed corrosion monitoring using magnetic measurement of current deflection

A Digital Lock-In Amplifier for Use at Temperatures of up to 200 °C

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