Frequency transducer of gas concentration in transistor structure with negative resistance

Abstract

The circuit of frequency transducer of gas concentration based on self-sustained oscillator was proposed. Results of the research of the frequency transducer of gas concentration with MEMS re-sistive element MiCS 6814, sensitive to the concentration change of combustible gases are reported.The dependencies of active and reactive components of the impedance ofthe frequency transducer of gas concentration on supply, control voltage and on gas concentration were calculated. Analytic expressions for transfer function and sensitivity equation were obtained.The sensitivity of transducer of gas concentrationchanges 645 Hz/ppm to175 Hz/ppm in the range 1 ppmto 1500 ppm. However, it substantiallydecreaseswith increasing propane concentration1500 ppm to9000 ppm and changes 175Hz/ppmto48 Hz/ppm within the range.