Yousef Hojjat - Faculty of Engineering, Tarbiat Modarres University,Tehran
amir abdollah - Faculty of Engineering, Tarbiat Modarres University,Tehran
Mohamadmorad Sheikhi - Faculty of Engineering, Tarbiat Modarres University,Tehran
Seyed shamsedin Mohajerzade - Faculty of Engineering, Tarbiat Modarres University,Tehran

In this research, a seismic sensor for sensing low frequency (less than20 Hz) with small amplitude (about 10 nanometers) is developed. The sensor is consisted of a (mass , spring) and an electrical transducer (strain gauge) to convert the strain to electrical output. In experimental model, flat springs are used and strain gauges are installed on them in a place, where the strain is the highest. The system resonates at target frequency, and resuets in the highest strain in springs and a high amplitude voltage. Using a proper filter, all outputs are eleminated, except the highest one is amplified by electrical circuit. In this research, due to low output of metallic strain gauges, semi-conductor strain gauge is used. The target frequency ( n ω ) is adjusted by changing the mass and/or the hardness of spring. Results of experiments show satisfactory operation of the transduser.

seismic sensor, seismic transduser, vibration sensor, mechanical vibration, strain gauge