Abstract: A device for measuring concentration of a constituent in blood includes: an irradiation unit for irradiating light toward a living body, the light having a wavelength disposed in a light absorption band of the constituent in the blood; a light receiving unit for receiving light, which is reflected in the living body or transmitted through the living body; and a concentration measurement unit for measuring the concentration of the constituent in the blood based on variation of light intensity of light received by the light receiving unit, the variation attributed to a pulse wave of the living body.

Abstract: A fuel property sensor is provided with three bypass passages and a measure passage. The measure passage is located inside of a closed loop which is comprised of common tangential lines of adjacent bypass passages and a part of profile line of each bypass passage in a cross section perpendicular to the measure passage. Even if the fuel property sensor is rotated around the axis of a fuel pipe in assembling the fuel property sensor to the fuel pipe, at least one of two bypass passages is always located above the measure passage in a vertical direction. Hence, bubbles included in the fuel are restricted from flowing into the measure passage. The fuel property sensor can detect the concentration of ethanol contained in the fuel with high accuracy.

Abstract: In a detection of an alcohol concentration, a first light and a second light are irradiated to a mixed liquid including a fossil fuel, an alcohol, and water, and the alcohol concentration is calculated based on amounts of the first light and the second light permeated through the mixed liquid. In the detection, a difference of a transmittance of the fossil fuel with respect to the first light and each transmittance of the alcohol and water with respect to the first light is larger than a first value. In addition, a difference of a transmittance of water with respect to the second light and each transmittance of the fossil fuel and the alcohol with respect to the second light is larger than a second value.

Abstract: An apparatus for detecting the concentration of particles in a liquid includes a light-emitting portion for emitting examination light which is totally reflected-by a boundary surface contiguous to the liquid to be examined, a photosensor for receiving the totally-reflected light, a reference sensor for directly receiving the examination light, and a judgment portion for finding the reflectance from outputs of the two sensors to compute the particle concentration. In case that the liquid to be examined is lubricating oil of an engine, the concentration of carbon particles is calculated, thereby judging the deterioration of the lubricating oil.