DIFFERENTIAL GRAVIMETRIC SENSORS FOR DETECTING VOLATILE ORGANIC COMPOUNDS EMITTED BY PLANTS AND PATHOGENS AND PROCESS FOR MAKING SUCH SENSORS

摘要

The invention relates to differential gravimetric sensors for detecting volatile organic compounds emitted by plants and pathogens and to a process for making such sensors. According to the invention, the sensor comprises a gravimetric detection device (DG1) capable of detecting the addition of mass produced by the gas molecules selectively adsorbed on its surface, a reference gravimetric device (DG2) insensitive to the detected gas and capable of response to temperature, humidity and ageing changes, a highly selective sensitive layer (PIM) deposited onto the surface of the gravimetric detection device, a reference layer (PNIM) insensitive to the gas detected by the sensitive layer, an electronic detection oscillator which contains in its positive reaction loop the gravimetric detection device and the frequence of which changes in proportion with the addition of gas molecules, an electronic reference oscillator which contains in its positive reaction loop the reference gravimetric device and the frequency of which is insensitive to the change of concentration of the volatile compound to be detected, and an electronic mixer (M) having at its input the signals received from the electronic detection oscillator and the reference oscillator and, at its output, a signal proportional with the frequency difference between the two oscillators.