A reading microscope is used to measure small distances or small distance changes. Its structure is divided into mechanical part and optical part, which is a telephoto microscope, mounted on a sliding table driven by a screw. This sliding table, together with the microscope, can be installed in different directions. Able to move forward, up and down, left and right; Or align below and move left and right. The sliding table is installed on a large base. The range of a reading microscope is usually a few centimeters, with a graduation value of {{0}}.001 centimeters. A common mechanical part of a reading microscope is manufactured based on the principle of a spiral micrometer, with 100 equal divisions on a dial plate linked to a screw with a pitch of 1 millimeter. Therefore, its graduation value is 0.001 centimeters. Another type is to use a measuring eyepiece with a 0.01mm scale to measure small displacements.

1. Install the reading microscope appropriately and align it with the object to be measured;

2. Adjust the eyepiece of the microscope to clearly see the forked wire (or ruler);

3. Adjust the aggregation of the microscope or move the entire instrument to make the image of the test object clear and eliminate parallax, that is, when the eyes move up and down, there is no relative movement between the image formed by the forked wire and the test object;

4. First align the fork wire with a point (or line) A on the object to be measured, and record the reading; Rotate the screw rod, align it with another point B, and then record the reading. The difference between the two readings is the distance between AB. Note that the screw rod must only move in one direction during two readings to avoid pitch differences.