Double radiation source assembly and transducer

An optical transducer for observing and/or measuring the concentration of a material component to be analyzed present in a medium, the transducer comprising:

• a radiation source assembly having first and second thermal radiation sources, the second radiation source being substantially transparent for radiation emitted by the first radiation source, the first radiation source being located in relation to the second radiation source, in such a position that the first radiation source emits radiation through the second radiation source;
• an absorption band filter located between the first and the second radiation sources, so that the radiation emitted by the first radiation source passes through the filter;
• and
• a radiation detector located to receive the radiation emitted by the first and second radiation sources,
• the radiation source assembly and the radiation detector forming a transducer unit, in which the radiation source assembly is spaced from the radiation detector by a given distance in the propagation direction of the radiation, whereby a measurement chamber containing the material component to be analyzed can be placed in the space between the radiation source assembly and the radiation detector,
• the absorption band of the absorption band filter substantially corresponding to the absorption distribution of the material component in the medium to be analyzed with the transducer;
• and
• each of said first and second thermal radiation sources of the radiation source assembly comprising a substrate having a recess and micro-filaments , which are fastened at their ends to a surface of the substrate to span said recess said micro-filaments having a radiation emitting region spaced at a distance from a bottom surface of the recess, whereby the transducer's electrical sampling frequency is at least about 5 Hz, preferably at least about 10 Hz, the rise time of a signal being at most about 50 preferably at most about 20 ms.