Method and device for measuring particles in a fluid stream

The Invention relates to a method for detecting electrically conductive Particles (20) in a in a pipe piece (10) having a Velocity (v) flowing liquid (16), wherein the liquid by means of a transmitter coil (18) with periodic alternating electromagnetic fields is applied, to induce eddy currents in the particles, by means of a through effective width (WB) and characterized as a coil arrangement (12, 14, 15) formed probe a periodic electrical signal is detected according to the eddy currents, the carrier wave a , whose amplitude and / or phase modulated by the particles , when the particles get into the effective width of the coil arrangement, wherein the sensor signal by means of a frequency-selective first filter unit (19) is filtered, the filtered by the first filter unit Signal by means of a triggerable A / D converter stage (35) is sampled , in order to obtain a demodulated digital measurement signal, the digital measurement signal by means of a digital frequency-selective, adjustable second filter unit (52) is filtered to a useful signal gain, and the useful signal is evaluated to the passage electrically conductive particles in the pipe piece to capture.