Patent ID: 7161677

Claim:
A condensation sensor comprising: at least one light transmitters configured to irradiate light in an irradiating direction from a light source; at least one photo-detector disposed to face the irradiated light of the light transmitters and configured to generate a signal output corresponding to an intensity of a beam of the irradiated light; and a condensate forming part including at least one transparent plate positioned between the light transmitters and the photo-detector so that the irradiated light is directed on a surface of the transparent plate on which a gas, when introduced to surround the transparent plate, condenses and forms a condensation film, wherein the condensation sensor is configured to detect forming of the condensation film on the surface of the transparent plate, based on a change in a time-course in the intensity of the beam of the irradiated light detected at the photo-detector through the condensation film on the transparent plate, the condensate forming part comprises a spacer formed from a thin plate and installed so that at least a portion thereof is fixed between a pair of the transparent plates, and a fixing unit fixing the spacer and the transparent plates, and the transparent plates forms a passage through which air flows between each gap formed by the transparent plates.