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Classification of measurement method

The measurement method is a method to obtain the measurement result according to a given measurement principle. The measurement method can be divided into different categories according to different measurement principles or measurement methods. Several common measurement methods are introduced below.

The direct measurement method is a method that can directly obtain the measured value, such as the measurement of the length of the part by the vernier caliper and the measurement of the diameter of the shaft by the micrometer.

Indirect measurement method is a method to obtain the measured value by measuring other quantities which have function relationship. For example, coordinate measuring machine, optical measuring machine and laser measuring machine are all indirect measurement methods.

Contact measurement method is a measurement method that the measuring equipment sensor contact the surface of the part. Common contact measurement methods include: vernier caliper, micrometer, measuring styli and joint arm measuring machine, etc. Contact measurement is very common in current industrial applications. It is characterized by high reliability, high accuracy and good repeatability. However, the disadvantage of contact measurement is that the measuring contact force may cause deformation to the measuring instrument and the surface of the part (such as soft surface), which can affect the uncertainty of measurement.

Non-contact measurement is a measurement method that the measuring equipment sensor do not contact the surface of the part. Common non-contact measurement methods include optical measurement, laser measurement, tool microscopy, etc. The advantages of non-contact measurement is measurement sensor is not in contact with the surface being measured, the parts to be measured surface will not pose any damage, more suitable for complex curved surface parts and soft surface measurement. Its disadvantage is the accuracy not as high as the contact measurement accuracy.