There are three types of mature MEMS accelerometers: piezoelectric, capacitive and thermal. Piezoelectric MEMS accelerometers use a piezoelectric effect. There is a rigid body supported mass inside, which has motion. In the case where the mass will generate pressure, the rigid body will strain and convert the acceleration into an 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 group is different from the surrounding air-conditioning, through inertia.
The thermal field change caused by the movement of the hot air mass causes the sensor to sense the acceleration value. Since the piezoelectric MEMS accelerometer has the existence of rigid body support, the piezoelectric MEMS accelerometer can only sense the "dynamic" acceleration. It can't sense the "static" acceleration, which is what we call gravity acceleration, while the capacitive and thermal senses can both sense "dynamic" acceleration and "static" acceleration.
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