This work presents a method implemented in an embedded system to detect the first contact between a high-speed machine tool and a workpiece surface with high accuracy, reliability and ease-of-use. This method is based on impedance magnitude variation measurements and the computation of a correlation function. A specific sensor was designed from this method for testing purposes in actual industrial conditions. This work is focused on the detection of the first contact between the tool and the workpiece surface. The purpose of this paper is to explore the efficiency of impedance spectroscopy and to identify a method to detect the first contact between a tool and a workpiece efficiently in high-speed machining operations and for the finishing process in particular.