International Journal of Engineering and Advanced Technology (IJEAT) ISSN: 2249 – 8958, Volume-9 Issue-3, February, 2020 1879 Published By: Blue Eyes Intelligence Engineering & Sciences Publication Retrieval Number: B3752129219/2020©BEIESP DOI: 10.35940/ijeat.B3752.029320 Eddy Current Testing Technique to Detect Imperfection Surface for Different Lift-off Value on Copper Metal Salmia Santa, Fauziah Sulaiman, Elnetthra Folly Eldy Abstract: Non-Destructive Testing (NDT) known as the evaluation of properties of a wide variety of materials without causing a damaged despite after inspection is done and the material still can be used. This paper aims for a designed NDT metal instrument that is conducted using eddy current testing (ECT) technique to find an applicable lift-off (LO) value in detecting imperfection. A dual sensor was designed consist of excitation coil was applied to evaluate the surface imperfections or other excitation frequencies in controlling the signal responses from the testing material, copper (Cu) with dimension of 100 mm x 100 mm installed with artificial surface imperfection (i.e., 7 mm, 14 mm and 21 mm) was main subject in this study. An established amplifier consisting of a specific op-amp was used to boost up the voltage of the alternate current (AC). The data of setting frequencies was ranged from 5.00 - 5.25 MHz was recorded varied of the LO values (i.e., 1.0 mm, 2.0 mm, 3.0 mm, 4.0 mm and 5.0 mm). Based on the frequencies applied the result for an applicable LO value acquires the promising result of reading signal was around 2 mm and the imperfection detection performance obtained a larger voltage gradient with the increase of the imperfection sizes. The study concludes that the developed non-destructive metal testing instrument of specific ECT design by using the excitation coil is appropriate in measuring the LO value and could be used to find different imperfection for metal. Keywords: Eddy Current Testing Technique, Lift-off, Metal Imperfection, NDT test. I. INTRODUCTION Non-Destructive Testing (NDT) known as the assessing the properties of a wide variety of materials without causing a damaged despite having been performed and the material still can be used. Eddy Current Testing (ECT) is one of the techniques based on electromagnetic induction principle. It had been widely applied in various NDT instruments in the early 20 th century and rapidly grow in industrial because of the user-friendly according to current developments and low cost of maintenance services. The noncontact, high- sensitivity and anti-interference capability of ECT system makes it important in many fields such as aerospace, metallurgy, electric power, machinery, nuclear and many more [1]. This technology of ECT method used to ensure the quality control for inspection according to the standards and to keep maintenance. ECT used a non-contact detection on imperfection surface but due to work the effect of Revised Manuscript Received on February 05, 2020 Salmia Santa, Department of MSc in Physic with Electronics at University Malaysia Sabah (UMS. Fauziah Sulaiman, Department of MSc in Physic with Electronics at University Malaysia Sabah (UMS. Elnetthra Folly Eldy, a lecturer in Universiti Malaysia disturbance from errors of variations in the distance between the sensor and testing material, known as LO effect caused by uneven surface whenever the eddy current detection is difficult to analyse the originality of the actual imperfection signal. In the recent years, research about LO effect has been focused whether in the field of probe design, a signal from the perspective of rationality and detection strategy, this variety of instrument testing designed to improve the detection accuracy. One important part of the LO effect was the used of proper or suitable frequency to acquire the promising result in imperfection detection on the testing material. Several studies regarding the use of frequency for LO effect, for instance, [2] development of a dual-frequency eddy current system based on quantity interference devices in defect detection by choosing appropriate excitation frequencies, but this design used to decrease the variance of LO effects. In other research by [3], a design of the eddy current method by using the sine wave oscillator circuit and sensor circuit to acquire an optimal frequency for the metal testing instrument. However, this design only able to find the optimal frequency on defect detection without emphasizing the signal output of the LO effect. Another research by [4] in which the development of the test instrument using the LO intersection point is distinguish by the discrete harmonic content of the initial pulse representation of the Fourier series. In result, this design makes a signal response varied by the LO effect but less sensitivity of defect detection that used an absolute coil or single test coil. Another study on LO frequency by [5] design the eddy current measurement using the LO curve and using the cable that connects to a network analyser and a conventional eddy current probe instead of improving the design of the test coil to monitor the shot peening surface conditions. Howbeit, this design only focused on measuring of material property and detect the condition of surface material tested that was less considering on defect detection. Aside from that, a study by [6] with design a reference phasor method based on reference voltage is proposed and implemented however this design makes only for suppressing the signal output of the LO effect on the probe coil voltage. Another study by [7] with design a magnetic field sensor (GMR sensor) under multi-frequency current excitation to analysed of amplitude and phase signals that allow the comparison of the different image quality strategies to show the defect even in presence of massive LO changes.