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High field resolution for nondestructive testing using sensitive magnetometers

Advanced image processing and flaw reconstruction algorithms of eddy current (EC) testing techniques are based on a low noise level of the measured response fields. Sensitive magnetometers such as SQUID and flux gate sensors provide a high field sensitivity of between 0.1 pT/√Hz and several pT/√Hz,...

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Bibliographic Details
Published in:Sensors and actuators. A. Physical. 2002-09, Vol.101 (1), p.85-91
Main Authors: Kreutzbruck, M.v., Allweins, K.
Format: Article
Language:English
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Summary:Advanced image processing and flaw reconstruction algorithms of eddy current (EC) testing techniques are based on a low noise level of the measured response fields. Sensitive magnetometers such as SQUID and flux gate sensors provide a high field sensitivity of between 0.1 pT/√Hz and several pT/√Hz, and an outstanding dynamic range of more than 150 dB/√Hz due to their read out electronics based on a feed back loop. The EC measurements based on a usual 12–16 bit data recording often result in an effective dynamic range of about 65–85 dB/√Hz, due to the quantization noise of the ADC. In the case of typical EC signal processing algorithms, such as subtraction of reference signals or phase rotation a higher dynamic range is required. We, therefore, set up an EC system based on sensitive magnetometer which covers an analog dynamic range of up to 160 dB/√Hz. We report on EC measurements with real 21 and 24 bit field resolution, on several aluminium samples and adapted signal processing for the separation of defect signals or the improvement of the spatial resolution.
ISSN:0924-4247
1873-3069
DOI:10.1016/S0924-4247(02)00186-3