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In many physical experiments, it is necessary to measure some small physical quantities. In order to accurately measure the small quantities, we need to amplify the small quantities by employing a suitable amplification method as mechanical amplification, optical amplification, electronic amplification and cumulative amplification.
The so-called “mechanical amplification” refers to amplifying the small quantity by using the geometric relationship in mechanical components. Spiral micrometer is a typical example of this method, which can accurately measure the tiny displacement along the axial direction by radian length of a larger radius. In general, spiral micrometer can effectively improve the measuring accuracy (more than 100 times). In addition, this method is also used in the high-precision measuring instruments, such as reading microscope and Michelson interferometer.
There are two commonly used optical amplification methods. One is to measure the small sub stance by visual amplification with optical instruments like magnifying glass, microscope, telescope and so on. The other one is to indirectly amplify the small quantities by optical instruments. For example, the optical lever amplifying method is used to measure the tiny variation of length or angle.
In physical experiments, some weak electrical signal variations (i. e. current and voltage) need to be measured or used to control some mechanical operations. Therefore, we can firstly amplify these weak electrical signals, and then observe for further control and measurement by some ordinary instruments. This is called the “electronic amplification method”. In general, the electronic amplification can be easily achieved by transistor or integrated circuits.
Cumulative amplification refers to the accumulation of tiny quantities with equal numerical variations, which aims to use conventional instruments to measure these tiny quantities. This method is often used for the thickness of paper or the quality of rice grains.