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Concept
Particle counter
Résumé
A particle counter is used for monitoring and diagnosing particle contamination within specific clean media, including air, water and chemicals. Particle counters are used in a variety of applications in support of clean manufacturing practices, industries include: electronic components and assemblies, pharmaceutical drug products and medical devices, and industrial technologies such as oil and gas.
Particle counters function primarily using the principles of light scattering, although other technologies may also be employed. Light scattering by particles use instrumentation comprising a high-intensity light source (a laser), a controlled media flow (air, gas or liquid) and highly sensitive light-gathering detectors (a photo detector).
Laser optical particle counters employ five major systems:
Lasers and optics: A laser operates on a single wavelength, so the light source is consistent with constant power output to illuminate the particle sampling region.
Controlled flow: The viewing volume is a small chamber illuminated by the laser. The sample medium (air, liquid or gas) is drawn into the viewing volume, the laser passes through the medium, the particles scatter (reflect) light, and a photodetector tallies the scattered light sources (the particles).
Photodetector: The photodetector is an electric device that is sensitive to light, and when particles scatter light, the photodetector observes the flash of light and converts it to an electric signal, or pulse. An amplifier converts the pulses to a proportional control voltage.
Pulse height analyzer (PHA): The pulses from the photodetector are sent to a pulse height analyzer (PHA). The PHA examines the magnitude of the pulse and places its value into an appropriate sizing channel, called bins. The bins contain data about each pulse, and this data correlates to particle sizes.
Black box: The black box, or support circuitry, looks at the number of pulses in each bin and converts the information into particle data.
Source officielle
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