The working principle of the accelerometer

The principle of the linear accelerometer is Newton's second law, which is the law of acceleration, that is, the balance of forces, A (acceleration) = F (inertial force) / M (mass). We only need to measure F. How to measure F? We can balance this force using electromagnetic force. This allows us to obtain the relationship between F and current. We just need to calibrate this proportional coefficient through experiments. Of course, the signal transmission, amplification, and filtering in between are matters of the circuit.
Most accelerometers work based on the principle of the piezoelectric effect.
The so-called piezoelectric effect is "For non-centrosymmetric crystals, the external force applied to the crystal not only causes deformation of the crystal but also changes the polarization state of the crystal, establishing an electric field within the crystal. This phenomenon, where mechanical force causes polarization in the medium, is called the positive piezoelectric effect."
General accelerometers utilize the characteristic of crystal deformation caused by acceleration. Since this deformation generates voltage, as long as the relationship between the generated voltage and the applied acceleration is calculated, acceleration can be converted into voltage output. Of course, there are many other methods to make accelerometers, such as piezoresistive technology, capacitive effect, thermal bubble effect, and optical effect, but their most basic principle is that acceleration causes deformation in a certain medium, and by measuring the amount of deformation and converting it into voltage output through related circuits. Each technology has its own opportunities and issues.
Piezoresistive accelerometers have developed the fastest due to their widespread application in the automotive industry. As safety increasingly becomes a selling point for car manufacturers, more and more additional systems are being added. The market size of piezoresistive accelerometers was about 420 million USD in 2000, and according to relevant surveys, it is expected to grow at an average annual rate of 4.1%, reaching 560 million USD by 2007. Among them, the European market is growing the fastest, as Europe is home to many airbag and automotive manufacturing companies.
Piezoelectric technology is mainly used in industry to prevent machine failures. Using this type of sensor can detect potential machine failures for self-protection and avoid accidental injuries to workers. This type of sensor has the repeatability, stability, and self-generation that users, especially those in the quality industry, pursue. However, in many new Applications, many users are still unaware of the use of such sensors. Vendors venturing into this undeveloped market will face many troubles, as end users are not well aware of the problems and solutions brought about by the use of such sensors.
If these issues can be resolved, it will promote the faster development of piezoelectric sensors. In 2002, the market value of piezoelectric sensors was 300 million USD, and it is expected that the annual growth rate will reach 4.9%, reaching 420 million USD by 2007.
Using accelerometers sometimes encounters distortion in output signals during low-frequency measurements. It is difficult to identify the cause of the faults using various measurement judgment methods. After analysis and summary, the main factors leading to distorted measurement results are: poor low-frequency response of the system, poor low-frequency signal-to-noise ratio of the system, and the influence of the external environment on the measurement signal. Therefore, whenever there is distortion in the low-frequency measurement signal of the accelerometer, compare the above three points to see which factor is causing it, and address it accordingly.