| 摘要 |
PROBLEM TO BE SOLVED: To obtain a fog detector which is small and low-cost, whose maintenance is not required and which can be handled simply. SOLUTION: An electrode 2 for moisture detection is provided. A heater 3 which is attached to the rear side of the electrode 2 is provided. A moisture detection circuit 4 which drives the electrode 2 is provided. A heater drive circuit 5 which drives the heater 3 is provided. A microcomputer 6 which controls the moisture detection circuit 4 and the heater drive circuit 5 is provided. In a fog judgment method, the temperature of the heater 3 is raised and lowered, the time 9 which elapses until the moisture output signal 7 of the moisture detection circuit 4 is change and the temperature are measured so as to be compared with reference data which indicates a correlation with the time, the temperature and the thickness of fog, which is found in advance, and the thickness of fog is judged.
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