What is the particle size measurement principle of the resistance method particle counter (Coulter instrument)?

  The particle size measurement principle of the resistance method (Coulter) particle counter is the principle of small hole resistance, as shown in Figure 3. The small hole tube is immersed in the electrolyte, and there is an electrode inside and outside the small hole tube, and the current flows from the anode to the cathode through the small round hole on the wall of the hole tube. The inside of the small-bore tube is under negative pressure, so the liquid outside the tube will flow into the tube. When measuring, the particles are dispersed into the liquid, and the particles flow with the liquid. When it passes through the small hole, the cross-sectional area of the small hole becomes smaller, the resistance between the two electrodes increases, the voltage rises, and a voltage pulse is generated. When the power supply is a constant current source, it can be proved that the peak value of the pulse is proportional to the particle volume within a certain range. As long as the instrument measures the peak value of each pulse, the size of each particle can be obtained, and the particle size distribution can be calculated from each pulse value.