Electrodynamic particle size analyzer

A method for determining a particle size distribution of a plurality of particles having a plurality of sizes by charging said plurality of particles and measuring a charge magnitude for each particle, the method comprising the steps of:

• a) charging each of said particles to a saturation level proportional to a particle dimension in a particle charging chamber having an exit passage that releases said charge-saturated particles from the charging chamber primarily one particle at a time;
• b) collecting any charged particles exiting the particle charging chamber through said exit passage and generating an electrical signal having a magnitude indicative of the charge of any such escaping charged particle;
• and
• c) using a distribution of the electrical signal magnitudes of a plurality of charged particles as an indicator of the particle size distribution.

A method for determining the particle size distribution in a sample containing a plurality of different size particles, the method comprising the steps of:

• a) establishing an electric field in a space between two electrodes;
• b) introducing the particles in said space;
• c) causing a charge to accumulate on said particles, said charge being proportional to the surface area of the particles, whereby said particles begin to oscillate between said electrodes under the influence of the electric field;
• d) allowing said charged particles to escape the space between said electrodes;
• e) capturing the escaping particles one at a time;
• and
• f) measuring the charge magnitude on each of the captured escaping particles.

A method for determining the particle size distribution in a sample containing a plurality of different size particles, the method comprising the steps of:

• a) establishing an electric field in a space between two electrodes;
• b) introducing the particles in said space;
• c) causing a charge to accumulate on said particles, said charge being proportional to the surface area of the particles, whereby said particles begin to oscillate between said electrodes under the influence of the electric field;
• d) allowing said charged particles to escape the space between said electrodes;
• e) capturing the escaping particles;
• f) measuring the charge magnitude of the captured escaping particles;
• and
• g) determining the frequency of occurrence of different measured charge magnitudes and correlating the measured charge magnitude to the surface area of the particles carrying the measured charges.

A method for determining the particle size distribution in a sample containing a plurality of different size particles, the method comprising the steps of:

• a) establishing an electric field in a space between two electrodes;
• b) introducing the particles in said space;
• c) causing a charge to accumulate on said particles, said charge being proportional to the surface area of the particles, whereby said particles begin to oscillate between said electrodes under the influence of the electric field;
• d) allowing said charged particles to escape the space between said electrodes;
• e) capturing the escaping particles;
• and
• f) measuring the charge magnitude of the captured escaping particles;
• further comprising between steps (d) and (e) a step of measuring a terminal velocity of the escaping charged particles and discriminating the presence of multiple particles.

A method for determining the particle size distribution in a sample containing a plurality of different size particles comprising the steps of:

• a) developing a calibration curve showing a surface charge distribution for a plurality of calibration particles having a known particle size distribution, by
• 1) charging each of said calibration particles by introducing said plurality of calibration particles in a space between a pair of electrodes, one of said electrodes having an orifice, in the presence of a static electric field;
• 2) collecting any charged calibration particles exiting said space through said orifice in said electrode and generating an electrical signal having a magnitude indicative of the charge of any such escaping charged calibration particle;
• and
• 3) storing the distribution of the electrical signal magnitudes of a plurality of charged calibration particles;
• b) charging a plurality of sample particles having an unknown particle size distribution by
• 1) charging each of said sample particles by introducing said plurality of sample particles in said space between said pair of electrodes in the presence of said static electric field;
• 2) collecting any charged sample particles exiting said space through said orifice in said electrode and generating an electrical signal having a magnitude indicative of the charge of any such escaping charged sample particle;
• and
• 3) comparing the electrical signal generated in step b(2) with the stored signal obtained in step a(4) to obtain a signal indicative of the actual sample particle size distribution.