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Evaluation of Optical Instruments for Real-Time Continuous Monitoring of Smoke Particulates
All instruments performed reliably with only minor problems. The manufacturers were prompt and helpful when needed.
MIE DataRam: The front panel keypad was not responding and was returned to the vendor and promptly fixed. The customer service was excellent.
Radiance Research: This instrument was considerably overestimating the Bscat reading. The vendor provided directions for cleaning the optics. Cleaning brought the nephelometer back into normal operating range. The vendor would have repaired the instrument if cleaning had failed. Radiance Research is a very small company. It took several days for the company to respond to the problem although they were very helpful once they responded.
Met One: The instrument was recalled for an upgrade and returned promptly. Service was excellent.
Optec NGN-3: No problems.
Andersen Aethalometer: No problems.
Accuracy and instrument comparison results are based on the two laboratory studies and the field tests. Accuracy was determined by comparing the average mass concentration to the gravimetric results for each test. The average mass concentration for an individual test was calculated by averaging the logged mass concentrations for the test duration. For instance, the MIE DataRam was programmed to average and log the mass concentration in 1-min intervals. For a 1-h test, the average mass concentration would be the average of the 60 logged values. The average test mass concentration for the gravimetric instruments was calculated by dividing the total accumulation of mass deposited on the filter by the total volume of air sampled. Instrument comparison results are determined by comparing the results from identical instruments.
Accuracy and instrument comparisons are broken down for each instrument. Comparison results were not available for the Optec NGN-3 and the Andersen aethalometer because only one of each instrument was available for testing.
Accuracy and instrument comparisons of each instrument type are judged by the least squares linear regression coefficients (slope and correlation coefficient R²) obtained for the number of samples (N). The intercept was forced to be zero for clarity. Each figure will show the appropriate data points, slope equation, and the correlation coefficient. For comparison purposes, a line has been drawn at 45 degrees, indicating the best possible one-to-one relationship.
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