抄録
We investigated the effect of environmental temperature on the counting efficiency of condensation particle counters (CPCs) by using a temperature-controlled chamber. The CPCs studied were TSI models 3010D and 3790, which were designed for automobile exhaust particle measurement with the nominal lower size detection limit (d50) of 23 nm. A set of counting efficiency measurements were conducted for particle sizes of 23, 41 and 55 nm at a temperature between 21 and 29°C. As a result, the counting efficiency of CPC 3010D showed linear temperature dependence for the particle size of 23 nm with the proportionality factor of -0.62 %/°C. Weaker temperature dependence was observed for particle sizes of 41 and 55 nm. On the contrary, the counting efficiency of CPC 3790 was not affected by the temperature for any particle sizes studied. Subsequently, the counting efficiency of CPC 3790 at 23 nm was repeatedly measured by changing the environmental temperature at the rate of about 15°C/h. We observed, at most, about 2 % reduction in the counting efficiency although there was a large scatter in the counting efficiency. These results suggest that we should control the environmental temperature for the calibration of CPC 3010D but there is no need for CPC 3790. However, since our experiments did not totally rule out the possibility of CPC counting efficiency dependence on rapid change in environmental temperature, use of a constant temperature chamber is recommended even for the calibration of CPC 3790.
