The most versatile and accurate particle sizing and counting analyzer available today. Using The Coulter Principle, also known as ESZ (Electrical Sensing Zone Method), the Multisizer 3 Coulter Counter provides number, volume, mass and surface area size distributions in one measurement, with an overall sizing range of 0.4 µm to 1,200 µm. Its response is unaffected by particle color, shape, composition or refractive index. The Coulter Principle is the absolute leading technology in high resolution and accuracy and it is further enhanced in the Multisizer 3 by using a Digital Pulse Processor (DPP). You will get the ultra-high resolution, multiple channel analysis and accuracy not provided by any other technology. It all makes the Multisizer 3 indispensable for any industrial or life science research project involving sizing and/or counting. Equally a powerful tool for quality control, it provides the analyst with a system which is easy to use, yet so technologically advanced that it is able to solve most particle sizing problems.
Principle
Particles suspended in a weak electrolyte solution are drawn through a small aperture, separating two electrodes between which an electric current flows. The voltage applied across the aperture creates a "sensing zone". As particles pass through the aperture (or "sensing zone"), they displace their own volume of electrolyte, momentarily increasing the impedance of the aperture.
This change in impedance produces a pulse that is digitally processed in real time. The Coulter Principle states that the pulse is directly proportional to the tri-dimensional volume of the particle that produced it. Analyzing these pulses enables a size distribution to be acquired and displayed in volume (µm3 or fL) and diameter (µm). In addition, a metering device is used to draw a known volume of the particle suspension through the aperture; a count of the number of pulses can then yield the concentration of particles in the sample.
Source: Beckman coulter