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A Portable Embedded Contactless System for the Measurement of Metallic Material Conductivity and Lift-Off

Rodrigues, N. ; Rosado, L. S. ; Ramos, P.M.

Measurement: Journal of the International Measurement Confederation Vol. 111, Nº 1, pp. 441 - 450, December, 2017.

ISSN (print): 0263-2241
ISSN (online): 0263-2241

Journal Impact Factor: 0,662 (in 2008)

Digital Object Identifier: 10.1016/j.measurement.2017.05.002

Abstract
This paper describes the development, implementation and characterization of a portable embedded measurement system for the contactless estimation of a metallic material conductivity and of the lift-off between the system probe and the metallic material surface. The system consists on an absolute probe with compensation and is capable of measuring the in-phase and in-quadrature components of the probe output voltage using as a reference the probe stimulus voltage. The stimulus module includes a direct digital synthesizer (DDS) to set the measurement frequency, while the acquisition module includes analog voltage amplification and analog-to-digital conversion. A microcontroller is used to control the measurement, process the acquired voltage samples, estimate the desired parameters and perform USB communication. The final dimensions of the pen-like system, its capability of communication with a smartphone and its ability to power the system from the smartphone make it highly portable and especially suited for non-destructive testing (NDT) and field measurements.