According to Zhihu's inquiry, when the piezoelectric crystal is subjected to external force, its interior will be polarized, and at the same time, charges with opposite signs will be generated on its two surfaces. The change of this charge is proportional to the applied force, so it can be used to measure the acceleration. In the piezoelectric acceleration sensor, the mass of the measured object or vibrating body will press on the piezoelectric element. When the mass vibrates, the generated force will be transferred to the piezoelectric element, causing the change of charge. By measuring the change of this charge, the value of acceleration can be obtained. Piezoelectric accelerometer has the advantages of high sensitivity, high precision and high reliability, so it has been widely used in aerospace, automobile, ship, earthquake monitoring and other fields.