To better understand the response and damage characteristics of structures under earthquakes, a great number of intelligent seismic sensors with high performance were needed to be installed distributed in the whole country. The intelligent seismic sensor was a cost-sensitive application because of its large number of usages. For this reason, a low cost intelligent seismic sensor was put forward in this paper. This kind of intelligent seismic sensor cut down the cost without sacrificing performance by introducing two three component MEMS accelerometers. It was composed by a microprocessor, two three component MEMS accelerometers, an A/D converter, a flash memory, etc. The MEMS accelerometer has better structure and frequency response characteristics than the conventional geophones'. But one MEMS accelerometer tended to be unreliable and have no enough dynamic range for precision measurement. Therefore two three component MEMS accelerometers were symmetrically mounted on both sides of the circuit board. And their measuring values were composed to describe the ground motion or structure response. The composed value was the in-phase stacking of the two accelerometers' measuring values, which enhanced the signal noise ratio of the sensor and broadened its dynamic range. Through the preliminary theory and experiment analysis, the low cost intelligent seismic sensor could measure the acceleration in accuracy.
