Infrared analyzer of constant radiant energy

Claim 1

Infrared analyser for determining the presence and concentration of a specific component in a liquid or gaseous sample comprising a source of radiant energy arranged to direct an infrared radiation beam against the sample to be analysed, and a detector arranged to receive said radiation beam downstream of the sample and provide a measurement of the concentration of the component under investigation in the form of an indication of the quantity of energy of infrared frequency absorbed by the said component during passage of the radiation beam through the sample, said detector comprising two thermistors both exposed to the radiation from the sample, in the case of one of them by way of screening means arranged to produce a different ohmic response by the two thermistors when energy is absorbed by said component, said thermistors being electrically connected into a balanceable bridge circuit provided with an instrument for measuring unbalance, so that said difference in ohmic response produces an unbalance in said bridge circuit which is indicative of the quantity of energy absorbed by said component and therefore of the concentration of the component in the sample under analysis, wherein said source of radiant energy is fed by the outlet of a comparator which receives as its respective inlets a reference signal of constant value and a signal which varies as a function of the sum of the instantaneous ohmic values of the two thermistors and therefore as the total radiant energy received by the detector.