A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperatures derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.

A diagnostic system for measuring temperature, pressure, CO.sub.2 concentration and H.sub.2O concentration in a fluid stream is described. The system may include one or more probes that sample the fluid stream spatially, temporally and over ranges of pressure and temperature. Laser light sources are directed down pitch optical cables, through a lens and to a mirror, where the light sources are reflected back, through the lens to catch optical cables. The light travels through the catch optical cables to detectors, which provide electrical signals to a processer. The processer utilizes the signals to calculate CO.sub.2 concentration based on the temperatures derived from H.sub.2O vapor concentration. A probe for sampling CO.sub.2 and H.sub.2O vapor concentrations is also disclosed. Various mechanical features interact together to ensure the pitch and catch optical cables are properly aligned with the lens during assembly and use.

A spectroscopic sensor assembly for detecting at least one predefined analyte constituent of a measurement fluid, the sensor assembly including a sensor housing; a radiation source; a detector device; a barrier assembly, which is transmissive for measurement radiation and is impermeable to the analyte constituent; a polymer matrix, which absorbs and releases the analyte constituent; a reflector assembly, which has a signal side facing the polymer matrix and facing the barrier assembly; the reflector assembly has a passage extending through the reflector assembly, through which passage the analyte constituent is exchanged between a measurement environment and the polymer matrix, which polymer matrix is located on the signal side of the reflector assembly; the reflector assembly reflects incident measurement radiation back toward the apparatus portion; the sensor assembly having a spacing means different from the polymer matrix that is designed to prevent the reflector assembly from approaching the barrier assembly.

According to an aspect of the present inventive concept there is provided a probe for analysis of a liquid in a mixture of the liquid and solid substance. The probe comprises: a tube comprising a sample end configured to be inserted into the mixture; a cap configured to come into contact with the mixture at the sample end, the cap comprising one or more openings configured for allowing passage of the liquid therethrough, and for preventing passage of the solid substance therethrough; and an optical measurement head arranged in the tube and configured to come into contact with the liquid having passed the one or more openings, wherein the optical measurement head is configured to collect measurement information for analysis of the liquid.

A fiber-optic transmission probe system for, for example, dissolution testing, includes a single probe, a single probe tip, and a number of pathlength adjusters of different lengths. The transmission probe system is usable to assemble different probe assemblies having different, desired optical pathlengths, where each probe assembly has either no pathlength adjuster or a different one of the pathlength adjusters. The probe system avoids the prior-art requirements of having either (i) multiple probes of different, fixed optical pathlengths or (ii) a probe with multiple probe tips of different, fixed lengths to achieve the different, desired optical pathlengths.