Matec, Inc.

Colloidal Dynamics Pty Ltd.

Colloidal Dynamics

Matec Applied Sciences, Inc.

David W Cannon

Richard W O'Brien

Tonis Oja

Gary L Petersen

Richard Wyndham O'brien

An apparatus for making pulsed acoustic measurements to determine particle size in a sample () such as a colloid. The apparatus includes two electrodes () between which an electric voltage is applied to the sample. The voltage is applied in short pulses. The applied voltage generates an acoustic signal, such as a sound wave (), in the sample which is detected with a transducer () after the wave () has passed through a delay element (). The delay element () is used to introduce enough of a time delay between the application of the voltage pulse and sound wave () reaching the transducer so that the received wave's signal can be isolated from any signal generated in the transducer () by the applied voltage. The delay element () and the transducer () are arranged into a geometry, or, alternatively, the delay element () is shaped, so that any reflections of the sound wave () from the sidewalls of the delay element () are deflected away from the transducer (). This reduces interference, particularly at low frequencies.

Geometry for pulsed acoustic measurements of particle size

An apparatus for determining the particle charge and size distribution of particles in suspensions of arbitrary concentration is provided. The apparatus includes a cell for application of an unsteady electric field or an unsteady mechanical force across the suspension of at least two different frequencies for accelerating the particles. The resulting acoustic wave generated by application of the electric field applied to the electrodes, or the electrical response and the acoustic pressure at the electrodes generated by application of the mechanical force is measured. Transducers convert the mechanical forces to electrical forces.

Device for determining the size and charge of colloidal particles by

This invention is concerned with a method and apparatus for measuring the electro-kinetic properties of a liquid which may be a mixture such as a slurry of particles, or a dispersion of droplets. Electrodes are placed in the liquid and an apparatus is provided for applying an alternating electrical potential to these electrodes. The electric field from this alternating potential acts upon the charged elements in the liquid, resulting in the generation of sound at the frequency of the applied electrical potential. By placing a conventional acoustic transducer in a spaced relationship to the electrodes, the acoustic signal is detected and measured. The amplitude of the acoustical signal will be a function of the electro-kinetic properties of the particles or emulsion droplets in the liquid. In its preferred form, the electrodes that are placed in the liquid have a spacial separation of one-half wave length, or odd integer multiples of half wave length of the sound which they generate. Coupled to the receiving transducer is a receiver that will amplify the signal to convenient levels. With this device a wide range of electro-kinetic measurements become possible even in highly concentrated systems.

Measurement of electro-kinetic properties of a solution

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Attleboro Falls, MA, United States of America

David W Cannon