| 摘要 |
PROBLEM TO BE SOLVED: To continuously perform dew point temperature measurement even in automatic cleaning control of one dew point meter, to eliminate the necessity of manual cleaning of a mirror surface and to eliminate the necessity of addition of a device for removing a condensed matter.SOLUTION: First of all, a first mirror surface cooling type dew point meter (dew point meter 1) is set as a dew point meter for measurement of initial operation and a second mirror surface cooling type dew point meter (dew point meter 2) is set as an auxiliary dew point meter in the initial operation. The dew point meter 1 periodically interrupts the dew point temperature measurement control during the dew point temperature measurement control to determine normality/abnormality of a mirror surface state, and when determining that the mirror surface state is abnormal, stops the dew point temperature measurement control and is shifted to automatic cleaning control. When the dew point meter 1 is shifted to the automatic cleaning control, the dew point meter 2 stops its automatic cleaning control and is shifted to dew point temperature measurement control. In the automatic cleaning control, a condensed matter which may be stuck to the mirror surface is evaporated or sublimated and removed. |
