G De Mey | PubMed Health

PubMed1991

Improved electronic gate technique, for particle counting and sizing in liquids.

Particle counting and measurements of particle size distributions in liquids can be based on pulse height analysis of signals obtained from a changing gate impedance, upon particle transition. Signal-to-noise ratio is markedly improved, making use of a four-electrode detector. An instrumentation amplifier with a high-pass filter is used as a preamplifier. Cylindrical electrodes and a coaxial aperture location result in a decreased detector capacitance, lowering the signal detection level and contributing to improved pulse shape. Volume sampling is flexible and accurate, making use of a stepping motor actuated digital sampling system. A newly developed baseline restorer, combined with a log-antilog amplifier circuit, allows for linearisation of the pulse height/particle size relationship.

Electronics↗

PubMedDate not supplied

Electric current distribution in tissues upon electrotherapy.

The authors have used computer simulations to study electric current distribution in tissues upon electrotherapy. The results are shown on a computer plot and apply to various types of current. Simulations on a simplified circular structure (as a model of a limb cross section) give a better understanding of the problem and clearly demonstrate the influence of electrode position and geometry. Simulations have established the possibility of directing the current density at particular internal areas. The greatest current density occurs close to the surface of the bone in an area midway between the electrodes, and larger electrodes may make treatment more effective. These conclusions are verified in the more realistic structure of a thigh cross section and extrapolation to a length section is made. Finally, the influence of metallic implants is considered. The conclusions of this work are of great practical interest to electrotherapy, particularly electrode techniques.

Computer Simulation↗