Instrumental particle counters

In instrumental particle counters, such as the well-known Coulter counter, the stream containing the particles is forced to pass through a flow... 

Optical particle counter An optical-electronic instrument for measuring the numbei" of airborne particles in different size ranges. 

The basic instrumentation in the present work is a Royco Model 225/518 High Concentration Particle Counter. The location of the air inlet and light sensing unit of the instrument in the card room has been described previously (2). The inlet was fitted with a vertical elutriator preseparator designed to prevent particles >15 vin aerodynamic diameter from entering the light sensor. Thus the collection efficiency of this instrumentation as a function of particle size should be similar to that of the Vertical Elutriator Cotton Dust Sampler. 

Aerosol Instrument Classification. Friedlander (34) classified the range of aerosol instrumentation in terms of resolution of particle size, time, and chemical composition. This classification scheme is illustrated in Figure 3. The ideal instrument would be a single-particle counter-sizer-analyzer. Operating perfectly, this mythical instrument would fully characterize the aerosol, with no lumping of size or composition classes, and would make such measurements sufficiently rapidly to follow any transients occurring in the aerosol system. 

Spectrex ILI-1000 Particle Counter combines the Prototron with a Particle Profile Attachment (multichannel analyzer). The instrument has been used [118] for examining volcanic ash. AC Fine Dust was used for calibration in eight 5 pm steps, which indicated that accurate data was obtained for sizes above 2 pm. It has also been shown to correlate well with the more tedious filtration and counting method for large volume parenteral liquids [119]. Although semi-transparent containers or liquids reduce the amount of transmitted light flux, the instrument gives valid data for particulates in oil [120]. 

Total particle levels should meet the required specifications and be measured, with the machine at rest, at defined intervals by means of a laser particle counter (or other suitable instrument) to demonstrate continued compliance. 

Observations of atmospheric nanoparticle number concentrations have increased greatly during the last five years. This advance has been made possible by new instruments and techniques that can measure particles with diameters as small as 3 nm. The new approaches include pulse height analysis of data from an ultrafme condensation particle counter (UCPC) (Stolzenburg and McMurry 1991 Wiedensohler et al. 1994 Weber et al. 1998b) and the combination of a nano-differential mobility analyzer (nano-DMA) (Chen and Pui 1997 Seto et al. 1997) with a UCPC. 

Particles, moisture, soot, heat, air, glycol, fuel, detergents, and process fluids are all contaminants commonly found in industrial lubricants and hydraulic fluids. However, particle contamination is widely recognized as the most destructive contaminant to the oil and machine. This is the reason why the particle counter is the most widely used instrument in oil analysis today. The central strategy to its success in reducing maintenance costs and increasing machine reliability is proactive maintenance. 

In this section, we briefly review three types of instruments, the optical particle counter, electrical aerosol classifier, and diffusion battery. These system.s are based on very dilTerent physical characteristics of the aerosols. The optical counters respond to signals from individual particles. The electrical analyzers depend on the measurement of a current carried by a slreaJTi of cbrnged aerosol particles. The ditfusion battery also depends on the behavior of particle clouds. The system often used to cover the size range from about 10 nm to 10 /jm is a combination of (a) the electrical analyzer up to about 0.2 jum and (b) the optical particle counter over the rest of the range. 

The limit of detection of an optical particle counter depends on instrument noise, Rayleigh scattering by the air molecules, and stray light resulting from imperfect optics. For commercial counters with an incandescent light source, the limit of resolution is about 0.3 /tm. Instruments with laser light sources can go down to about 70 nm. 

Quantitative analysis of FTIR spectra series recorded during AIDA expansion cooling experiments allows for deriving time profiles of the number concentration of the ice crystals as well as the ice water content (IWC). This provides a unique possibility to validate the independent measurements of these quantities with the optical particle counter as well as the FISH and TDL instruments, as demonstrated on the right side of Figure 4. The upper panel... 

ISO 11171 specifies calibration parameters for instruments and sensors. Repeatability and reproducibility of particle counters are ensured by a traceable standard such as provided by the National Institute of Standards and Technology (NIST). The medium test dust (MTD) reference fluid SRM-2806A is used to certify that particle counters correctly determine the count and size distribution of particles. The ISO 11171 standard specifies the maximum allowable percent differences in particle counts between test runs. Only counters that are certified as passing the ISO 11171 standard should be used for oil condition monitoring [27]. 

Calibration should be traceable to national or international standards through an unbroken chain of comparisons. For instrumentation affecting sterility control in aseptic manufacturing facilities this usually involves comparison of values measured with the item of equipment under test, say a particle counter or a pressure differential gauge, with values measured with a standardized device. In many cases this may mean the use of external contract calibration services, with all that this implies in relation to assuring that the contractor s calibration control systems are themselves under good control. 

Particle counters are not easily disinfected for taking into aseptic filling rooms. They may be dedicated to particular areas, or remote instruments with mobile or fixed sampling tubes can be purchased. 

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