Microprocessor Controlled Particle Counter System

Alvin Lieberman

Abstract

Operation of an optical particle counter with microprocessor control of particle size calibration and data recording is described. Sensors are available to measure particles O.1 μm and larger. A system with a range from 2 μm to 125 μm will be described. Calibration data based on response to monosized particles are stored in the system memory, along with sensor resolution information and system changes since the last calibration. The instrument adjusts the particle size channels internally for the selected calibration base particles. Once calibrated, the instrument can be set to report data in operator selectable sizes or any of four default particle size groups. Three default groups are based on pharmaceutical and hydraulic fluid power industry standards and one is set in a logarithmic spread of 16 particle sizes that covers the system dynamic range. A front-panel keyboard and CRT display allow selection and control of all operating parameters. These include reported size ranges, liquid sample size, number of sample replications (including suspect sample rejection), data averaging, and comparison of data from two sensors. Differential or cumulative data can be reported in tabular or histogram format. Data can be sent to an internal thermal printer or to an RS-232C output.

Received July 31, 1989.
Accepted December 13, 1989.

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