Electric Sensing Zone, also referred to as the Coulter Technique or Coulter Counter, is a true high-resolution, high-speed particle counter and particle size distribution analyzer. It covers a nominal span of about 1.0 µm to 260 µm; under special circumstances, this lower detection level can be reduced to about 0.4 µm. Data is typically presented to our clients on a Frequency (Population) and Volume (Mass) basis vs. Size. Being a true particle counter, the instrument can also be used to determine the concentration of Particles/mL of Fluid vs. Size.
During this process, particles suspended in a conductive fluid (aqueous or organic) are drawn through a precision sapphire aperture, on either side of which are two platinum electrodes. A current is impressed upon the electrodes, resulting in a constant voltage across the aperture. Upon the passage of a particle through the aperture, a voltage pulse is generated due to the change in electrolyte resistance. The change is proportional to the volume of the particle, determining the envelope volume of a particle in three dimensions. The signal is counted as one event (i.e. particle count) while, simultaneously, the volume is directly determined.
Because there are no optical theories of light involved in the measurement principle, data presented on the basis of Equivalent Spherical Diameter is enhanced.