Abstract
Lift-offs of the sensor could significantly affect the measurement signal and reconstruction of material properties when using the electromagnetic (inductive) eddy current (EC) sensor. Previously, various methods (including novel sensor designs, and features like zero-crossing frequency, lift-off point of intercept) have been used for eliminating the measurement error caused by the lift-off distance effect of the sensor. However, these approaches can only be applied for a small range of lift-off variations. In this article, a linear relationship has been found between the sensor lift-off and ratio of dual-frequency EC signals, particularly under the high working dual frequencies. Based on this linear relationship, the lift-off variation can be reconstructed first with a small error of 2.5% when its actual value is up to 10 mm (10.1% for 20 mm). The reconstructed lift-off is used to further get the property of the material under a low single frequency. Experiments on different ferrous metals have been carried out for the testing of the reconstruction scheme. Since the inductance is more sensitive to the material property (and less sensitive to the lift-off) under low frequencies, the reconstruction error of the material property is much smaller than that of the lift-off, with 1.4% under 12 mm (and 4.5% under 20 mm).
Highlights
A S ONE of the promising and general techniques for nondestructive testing, eddy current (EC) testing has been widely applied for the health checking, flaw inspection, fatigue scanning (e.g., the rolling contact fatigue (RCF) of rail strip), deep exploration, and properties measurement [1]–[9]
The fluctuating noise signal exists under the lower frequency spectrum (10–1 kHz) due to the low signal-to-noise ratio (SNR) of the instrument
Based on the dualfrequency linearity of lift-off (DFL) feature, an algorithm has been proposed for the reconstruction of the sensor lift-off
Summary
A S ONE of the promising and general techniques for nondestructive testing, eddy current (EC) testing has been widely applied for the health checking, flaw inspection, fatigue scanning (e.g., the rolling contact fatigue (RCF) of rail strip), deep exploration, and properties measurement [1]–[9]. Various approaches have been proposed to address the lift-off issue on the electromagnetic property measurement of conductive samples, which mainly involves the different sensor designs, measurement techniques and features, and data-processing methods. Both the peak frequency feature, zero-crossing feature, and phase feature of the inductance have been proposed for eliminating the lift-off effect on the property measurement of the sample when using both SEC and MEC sensors [26]–[36]. These methods are focusing on reducing the lift-off effect instead of directly getting the liftoff value. For the measurement of using large sensor lift-offs (e.g., over 14 mm), the property reconstruction is even more accurate under slightly lower dualfrequency combinations
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callMore From: IEEE Transactions on Instrumentation and Measurement
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
