Inventors:
Dennis J. Knowlton - Boulder CO
Edward R. Green - Boulder CO
Assignee:
Particle Measuring Systems - Boulder CO
International Classification:
G01N 1514
Abstract:
Noise reduction is effected by multiplying together electrical signals that include pulses embedded in noise, with the pulses being indicative of the same event, such as light scattered by particles, occurring at a viewing area, and with the signals being processed prior to multiplication so that the pulses and the variance of the noise in the electrical signals are multiplied by one another. A detector in each of a plurality of channels detects the events occurring at the common viewing area and provides pulses indicative thereof, and the output from each detector is amplified, passed through matched low-pass filters to enhance pulse detection, and then passed through a baseline restorer to remove DC components from the noise then present in the signal, prior to coupling of the signals to a multiplier. At the multiplier, peak values of the pulses included in the signals from each of the channels multiply, as do the variances of the uncorrelated noise included in the signals from each of the channels, resulting in multiplication of the signal-to-noise ratio, and hence improvement in signal-to-noise.
