A gas analysis device includes a probe tube, a flange, an optical system member, and heaters. The probe tube includes an optical path through which measurement light is projected onto a prescribed measurement region of a sample gas flowing through a flue and/or is received from the measurement region. The flange is fixed to the outer periphery of the probe tube and is attached to a pipe side wall. The optical system member projects measurement light onto the sample gas S within the measurement region and/or receives measurement light from the measurement region. The heaters are disposed within the flange and heats the portion where the probe tube and flange are fixed to each other.

An apparatus for detecting one or more properties of a downhole fluid includes a housing. The apparatus also includes a location-sensitive optical detector, arranged within a chamber formed by the housing. The apparatus further includes a light source, arranged within the chamber. The apparatus also includes a lens, positioned at an end of the housing, the lens preferably having a flat side and a curved side, the flat side positioned proximate the chamber to position the flat side closer to the light source than the curved side. The apparatus further includes a mirror, arranged outside the housing.

A sensor head assembly for a measurement system for powderised agent includes: an elongate body having a proximal end configured to receive a fibre optic cable, and a distal end; a sensing chamber provided within the elongate body, a first window provided at a proximal side of the sensing chamber and a second window provided at a distal end of the sensing chamber; and a concave mirror mounted within the elongate body at a distal side of the second window, wherein the concave mirror is mounted such that its position within the elongate body is adjustable.

A spectroscopic assembly may include a spectrometer. The spectrometer may include an illumination source to generate a light to illuminate a sample. The spectrometer may include a sensor to obtain a spectroscopic measurement based on light, reflected by the sample, from the light illuminating the sample. The spectroscopic assembly may include a light pipe to transfer the light reflected from the sample. The light pipe may include a first opening to receive the spectrometer. The light pipe may include a second opening to receive the sample, such that the sample is enclosed by the light pipe and a base surface when the sample is received at the second opening. The light pipe may be associated with aligning the illumination source and the sensor with the sample.

A method for determining contents of sample liquids spectrometrically includes an empty-state measurement with no liquid present, to obtain an empty-state light intensity measurement I.sub.e. A liquid-blank measurement is then taken of a pure unmixed volume of said liquid component, to obtain a liquid-blank light intensity measurement I.sub.w. A sample measurement of the sample liquid is then taken to obtain a sample light intensity measurement I.sub.s. Using I.sub.e, I.sub.w, and I.sub.s, determination is made of a volume concentration of a liquid component [H2O] in the sample liquid, and a liquid-corrected light intensity measurement I.sub.wc. From I.sub.s, I.sub.wc and a known length of the light path, a volume concentration of alcohol [Alc] is calculated. From [H2O] and [Alc], a remnant volume concentration attributable to other constituents is determined, from which a carbohydrate concentration [Carb] is calculated using a predetermined carbohydrate coefficient. Provisions for turbidity determination and light scatter correction are included.