A method and apparatus to detect non-cancelled magnetic field produced when current flows through an electric conductor are provided. The materials are mixed by passing them through an ultrasound horn vibrating in resonance, having an internal chamber. The first protruding portion is connected to one end of the first positioning portion, and the second side wall is connected to another end of the first positioning portion. Each row includes a value from CV1 and a value from CV2. The main characteristic of the inventive syringe is that the tube has a cylindrical upstream part in which the means retaining the particles are fixed, said upstream part having a substantially constant cross-section over a length that is more than twice its inner diameter. The display includes an optical element and a light source to indicate the sensed presence of the live electrical wire.