[Sulaiman* 6(8): August, 2019] ISSN 2349-4506 Impact Factor: 3.799 Global Journal of Engineering Science and Research Management http: // www.gjesrm.com © Global Journal of Engineering Science and Research Management [16] OPTIMAL FREQUENCY DESIGN OF EDDY CURRENT TESTING FOR COPPER, BRASS AND MAGNESIUM ALLOY METAL WITH DIFFERENCE THICKNESS Fauziah Sulaiman*, Elya Alias, Abu Bakar Abdul Rahman, Salmia Santa, Elnetthra Folly Eldy *Physics with Electronics Program, Faculty Science and Natural Resources, Universiti Malaysia Sabah,Jalan UMS, 88400 Kota Kinabalu Preparatory of Science and Technology Centre Universiti Malaysia Sabah,Jalan UMS, 88400 Kota Kinabalu DOI: 10.5281/zenodo.3372507 KEYWORDS: Results for Nondestructive Test of Metal Imperfection of Copper (Cu) Metal, Results for Nondestructive Test of Metal Imperfection of Brass Metal. ABSTRACT The main objective of this paper is to find the optimisation frequency for a designed non-destructive testing (NDT) metal instrument known as eddy current testing (ECT). The chosen materials were copper (Cu), brass and magnesium alloy (Mg) metals in 100 mm X 100 mm dimension, and with different type of thickness, i.e. 1.5 mm, 3 mm and 5 mm. All of the three (3) different kind of thicknesses in each metal were installed with artificial defect and were tested to identify the optimal frequency. A dual-sensors were designed and established to gather the voltage output with input frequencies were ranged between 250 kHz - 3.5 MHz. The output signals of the voltage of testing from the sensor circuit then compared to analyse the optimal of range frequency for the testing instrument. The result of this research showed that the non-destructive metal testing instrument of dual-sensors by using ECT method can be used to find different defect for these metals, i.e. copper (Cu), brass and magnesium alloy (Mg). The optimal frequencies for copper was 2.95 , brass was 2.90  and magnesium was 2.89 . The categorisation of thickness on metal for the ECT instrument is suitable at 2.95  for copper, 2.90  for brass and 2.89  for magnesium alloy, which also known as the optimal frequency. INTRODUCTION EDDY current technique is an important electromagnetic of non-destructive technique (NDT) evaluation that is widely used in many industries for detection of surface cracks and corrosion in components made of metallic materials. 1 One reason for this is that general purposes, user-friendly eddy current instruments are a relatively recent phenomenon. 2 There are some advantages on using eddy currents for NDT purposes. It is quick, simple, and reliable inspection technique to detect surface and near-surface defects. Besides, it is also can be used to perform several tasks like thickness measurements, electrical corrosion valuation, and magnetic permeability measurements. 3 There is no need for consumables and the inspection surface preparation is minimal and results are drawn immediately. Eddy current could be made by high frequency magnetic field. The magnetic field happens when high frequency alternating current enters primary or transmitter coil. 4 In case there is continuous space inside the test material, the eddy current will be higher. The eddy current will be lower if there are no continuous space inside the test material. 5 This different could be used to measure the continuity of the test material by using eddy current. In this method, the current in the coil that constitute the probe induces eddy currents in the test material based on the basic principle of electromagnetic induction. 6 When a crack interrupts the eddy current flow, the result is change of the coil impedance, by measuring these impedance changes or by measuring a resultant magnetic field using a coil sensor it is possible to detect the cracks in the test material. In order to ensure the basic study of NDT in eddy current testing strengthen, the non-destructive metal testing instrument by using eddy current method which consisted of 50  ohm ground function generator which can