Basic tools for length measurement

The basic tools for measuring length are ruler, tape measure and vernier caliper.

1, ruler

A ruler, also called a middle ruler, has a precise straight edge and is used for measuring length and drawing. Widely used in mathematics, measurement, engineering and other disciplines. Rulers are used to measure straightness and flatness by light gap method, and can also be used to check length and size together with measuring blocks.

2. Tape measure

Tape measure is a common measuring tool in daily life. What we often see is a steel tape measure, which is often used in construction and decoration, and is also one of the necessary tools for families. Divided into fiber tape measure, tape measure, waist measure and so on.

The tape measure can be rolled up because it has a spring. When measuring the length, the length of the ruler and the spring is actually lengthened. Once the measurement is completed, the spring in the tape measure will automatically shrink, and the ruler will also shrink under the action of the spring force, so the tape measure will be rolled up.

3. Vernier caliper

Vernier caliper is a measuring tool for measuring length, inside and outside diameter and depth. The vernier caliper consists of a main ruler and a sliding vernier attached to the main ruler. As a common measuring tool, vernier caliper can be used in the following four aspects: measuring workpiece width, measuring workpiece outer diameter, measuring workpiece inner diameter and measuring workpiece depth.

Ordinary vernier calipers can be divided into three types according to their accuracy: 0. 1mm, 0.05mm and 0.02 mm. ..

Basic components of length measurement:

1, known length

In the value transmission of length measurement, the length and angle verified by the transmission system, such as the scale on the linear scale in the length meter, the laser wavelength in the laser interferometer, the length and angle composed of dense lines on the long and round measuring gratings respectively, and the angle formed between the two measuring planes of the angle gauge block, etc.

Some geometric quantities with precise shapes. For example, the optical measurement plane of flat crystal, the laser beam in laser collimator, the involute trajectory produced by the base plate and scale mechanism in involute measuring instrument, and the circular trajectory formed by the precision shafting of roundness instrument.

2. Positioning and aiming

It is used to determine the relative position of the measured length and the known length, so as to compare them correctly and obtain an accurate value. There are two ways of positioning and aiming: contact and non-contact.

3. Enlarge and subdivide

Enlarge and subdivide the smallest unit length in the known length, so that it can accurately distinguish the small difference between the known length and the measured length, mainly including mechanical, optical, pneumatic, electrical and photoelectric.