Abstract: An ultraviolet irradiation unit of the present invention includes a casing, a light source emitting ultraviolet rays arranged in the casing, an ultraviolet transmitting body arranged between an ultraviolet emission opening of the casing and the light source. The casing has an outer diameter dimension that enables the casing to fit within a bore of a joint connected to a flow channel pipe.

Abstract: A flow rate measurement device includes a channel; a flow detection part disposed at the channel, the flow detection part including an impeller configured to be rotated by a flow of the fluid and a reflection part disposed at the impeller and configured to reflect light; a light source configured to emit light toward the reflection part; and a detection part configured to receive light emitted from the light source and reflected by the reflection part. A width of a detection surface of the detection part intermittently or continuously changes in a movement direction of the reflection part along with rotation of the impeller as viewed in a direction orthogonal to a rotation axis of the impeller, or a width of a reflection surface of the reflection part intermittently or continuously changes in a rotational direction of the impeller.

Abstract: An ultraviolet irradiation unit of the present invention includes a casing, a light source emitting ultraviolet rays arranged in the casing, an ultraviolet transmitting body arranged between an ultraviolet emission opening of the casing and the light source. The casing has an outer diameter dimension that enables the casing to fit within a bore of a joint connected to a flow channel pipe.