There are three types of mature MEMS accelerometers: piezoelectric, capacitive, and thermal. Piezoelectric MEMS accelerometers use a piezoelectric effect. There is a rigid mass supported inside. When there is motion, the mass will generate pressure, the rigid body will generate strain, and the acceleration will be converted into electrical signal output.
There is also a mass inside the capacitive MEMS accelerometer, which is a standard plate capacitor from a single unit. The change of acceleration drives the movement of the moving mass to change the spacing and the facing area of the two poles of the plate capacitor, and the acceleration is calculated by measuring the amount of capacitance change.
The thermal MEMS accelerometer does not have any mass inside. It has a heating body in the center, and the temperature sensor is around. The inside is a closed air cavity. Under the action of the heating body, the gas forms a hot air mass inside the hot gas. The proportion of the mass is different from the surrounding air-conditioning. The thermal field change caused by the movement of the inertial hot air mass causes the sensor to sense the acceleration value.
Since piezoelectric MEMS accelerometers have rigid body support inside, piezoelectric MEMS accelerometers can only sense “dynamic” acceleration, but can not sense “static” acceleration, which is what we call gravity acceleration. . Both capacitive and thermal sensing can sense both “dynamic” acceleration and “static” acceleration.
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