Abstrak Sensor arus eddy (eddy current) digunakan untuk pengukuran ketebalan logam khususnya logam non magnetik seperti alumunium.  Penelitian ini telah mengembangkan sensor eddy current berbahan PCB (printed circuit board) jenis FR4 yang memiliki ketebalan lapisan tembaga 35micron. Prototipe yang dihasilkan mempergunakan koil sensor dengan jumlah gulungan (n) 30 lilitan, diameter (Æ) 30mm, lebar dan jarak antar koil, (dkoil) 0,254mm dan tahanan (Rkoil) sebesar 4,26Ω. Respon sensor ketebalan pelat logam terhadap bahan uji dievaluasi dengan memberikan eksitasi frekuensi tunggal 700Khz, 1MHz dan 1.33MHz. Rangkaian ketebalan pelat telah mempergunakan rangkaian pengunci fasa (phase locked loop) dan mampu mengukur variasi ketebalan  mulai 0,2 mm sampai 2 mm, sementara jarak antara sensor dengan logam uji dijaga konstan 2 mm. Hasil pengukuran memberikan respon kurva U(t) dalam hubungan Kata-kata kunci:sensor eddy current, PCB FR4, material non magnetik, ketebalan logam, rangkaian phase locked loop Abstract Eddy current sensor is used to measure the thickness of metals, especially non-magnetic metals such as aluminum. This research has developed eddy current sensor made from PCB (printed circuit board) type FR4 which has 35micron copper layer thickness. The developed prototype uses a designed coil sensor with the number of winding (n) 30 turn, diameter () 30mm, width and distance between coils, (dkoil) 0.254 mm and coil resistance (Rkoil) of 4.26 Ω. The sensor response to the test material was evaluated by giving a single frequency excitation of 700 Khz, 1 MHz and 1.33 MHz. The plate thickness electronics has used a phase locked loop circuit and is capable to measure the thickness variations from 0.2 mm up to 2 mm, while the distance between the sensor coil and the test object was kept constant at 2 mm. The measurement results give the U (t) curve response in the exponential relationship. Keywords: eddy current sensor, PCB FR4, nonmagnetic material, thickness, phase locked loop circuit