To measure, record, and analyze the vibration and movements of the earth, structures, as well as exploration of underground reserves and study the behavior of the structure of the earth layers, this sensor was designed.
Various methods such as changes in resistance, capacitance or electrical induction, and other physical principles can be used to measure the motion of a suspended mass relative to the base. Based on these same physical principles, various types of seismic sensors such as geophones, seismographs, and accelerometers have been developed that measure the displacement, speed, or acceleration of the earth's motion. Seismographs and geophones measure displacement or velocity, and accelerometers measure the acceleration of the earth.
One of the methods used to measure acceleration is the use of force balance accelerometers or servo accelerometers. These types of accelerometers require a force to balance a mass suspended in relation to the frame or shell of a sensor. The coil generates the suspended force generated in a constant magnetic field. Therefore, these sensors include a mass-spring system and a feedback control unit (feedback), and a power-generating coil. The different types are made in a variety of feedback units and forces such as piezoelectric types, differential capacitors, and LVDT coil, which includes different types of displacement transducers. The task of the control unit (coil) and the feedback is to detect the movement of the mass and to produce a proportional current for feeding the coil to apply force to the mass and keep it in the neutral state.
In this invention, a differential capacitor is used for the sensor feedback unit, which has high sensitivity while being simple and cheap to make. These types of accelerometers have a large dynamic range and designed to have a linear response in very low frequencies. The idea and the novelty here is to use an array of capacitors instead of a single capacitor. This way the difference between the capacity of the planner capacitors can be used for sensing the displacement of the mass with more sensitivity.