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| Titel: |
Intrinsic Calibration of the Pollak Counter—A Revision |
| Auteur: |
Sinclair, David |
| Verschenen in: |
Aerosol science and technology |
| Paginering: | Jaargang 3 (1984) nr. 2 pagina's 125-134 |
| Jaar: |
1984 |
| Inhoud: |
The “intrinsic” calibration of the Pollak condensation nucleus counter was reevaluated with the aid of a “tube bridge,” the device invented by Pollak for this purpose. This device allows measurement of the concentration of an aerosol and then another measurement when the concentration has been reduced to exactly one-half. This is accomplished by filtering out all of the aerosol from one of the two legs of the tube bridge, while maintaining the same flow rate in each. Seven hundred and eighty pairs of measurements were made over the concentration range of 102/cm3 to 106/cm3 using the aerosol in the laboratory ambient atmosphere, gold aerosol from a thermal generator, and carbon aerosol from the incomplete combustion of methane. The results gave the ratio, half to full aerosol, equal to 0.50 ± 5% over the range from 10/cm3 to 105/cm3. Above 105/cm3 the ratio increased to about 0.7 depending on the type of aerosol but not on the particle size. These values were obtained from Pollak's 1960 calibration tables commonly in use. On the basis of the above measurements a new calibration table was made for concentrations above 105/cm3. The revised concentrations for gold are as much as 60% higher than Pollak's values and those for carbon become two or three times greater. We believe Pollak's values are in error because he measured the aerosol from a balloon in which the concentration was continually decreasing. We found it almost impossible to obtain sufficiently accurate measurements when the aerosol concentration was decreasing. This is particularly true when the concentration is decreasing rapidly as was the case at the higher concentrations measured by Pollak. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 7 van 11 gevonden artikelen
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