A/s N. Foss Electric

Aktieselskabet Bruel & Kjaer

Sten A Nexo

Jorgen Christensen

Andreas S Frandsen

Henrik R Andersen

Ib E Jorgensen

A photoacoustic gas analyzer comprising a measuring chamber, a modulated light source, and at least one microphone in connection with the measuring chamber and measuring the changes of pressure caused by the absorption of the light in the chamber. The measuring chamber comprises an inner surface with a reflecting coating. The measuring signal is thereby proportional to the gas concentration and is not provided as the difference between two almost equal values. As a result it is possible to measure small gas concentrations provided the light intensity within the measuring chamber suffices.

Photoacoustic gas analyzer

Fat in a fat-containing sample, in particular a milk sample, is determined quantitatively by infrared absorption technique, using as sample waveband a band characteristic to carbon-hydrogen bonds, instead of the conventional triglyceride carbonyl band. This avoids the dependency of the measured result on the fat composition of the sample. Influences from other components in the sample are compensated for. A preferred method uses double wavelength determination, with sample wavelength in the interval from 3.475 to 3.51 .mu.m and reference wavelength in the range between 3.51 and 3.60 .mu.m.

Method for quantitatively determining fat in a fat-containing sample

An apparatus for measuring components of liquid samples, such as milk samples, based on the ability of these components to absorb infrared radiation at certain frequencies. A single radiation beam is directed through a cuvette containing the sample, and the apparatus comprises a plurality of pairs of optical filters. Each of these pairs is associated with a respective one of the components to be measured and comprises a component filter for passing infrared radiation at a narrow frequency band at which the radiation absorbing ability of the said component is relatively high, and a reference filter for passing infrared radiation at a different narrow frequency band at which the radiation absorbing ability of the component is lower. A component of the sample is measured by successively positioning the filters of the associated pair of filters in the radiation beam between the radiation source and the cuvette, and the radiation passing the cuvette is detected by a detector, preferably a thermopile radiation detector of the monolithic type, and the content of the respective component is calculated on the basis of the signals received from the detector. The radiation beam is chopped by means of conventional chopping means, and each of the filters is preferably retained in the radiation beam in a period of time comprising a plurality of cycles of the chopping means.

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Birkerød, Denmark

Sten A Nexo