Electric Sensing Zone is also referred to as the Coulter Technique or Coulter Counter. The instrument is a true high resolution, high speed particle counter and particle size distribution analyzer that covers a nominal span of about 1.0 µm to 260 µm. Under special circumstances, the 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.
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 constant current is impressed upon the electrodes which results 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. Therefore, the analytical method determines the envelope volume of a particle in three dimensions which is the instruments claim to fame. The signal is counted as one event (i.e. particle count) and simultaneously, the volume is directly determined. Also, data presented on the basis of Equivalent Spherical Diameter is enhanced because there are no optical theories of light involved in the measurement principle.
PTL uses the following Electric Sensing Zone instruments: