A gear is a rotating circular machine part having incising or, in the case of a cog or bull gear, inserting teeth (called a cog) which meshes with another (compatible) toothed part to transmit (convert) torque and speed. The fundamentals behind how gears work are similar to the fundamentals of a lev

In terms of measuring sensors, although high-precision circular gratings are generally used for angle measurement, length measurement varies with different objects. For gears with high accuracy requirements or workpieces with long axial dimensions, dual frequency (or single frequency) laser interferometer is generally used as the length reference (such as measuring involute or spiral template); In other cases, high-precision long gratings are used.