The accuracy of the measurement results of the three-dimensional measuring instrument is one of the four elements of measurement, in order to achieve a correct and reliable measurement, it must follow the basic principles of geometric quantity measurement?

1. Abbe principle The measurement axis of the measured quantity coincides with or is on the extension of the measurement axis of the standard quantity, which is called the Abbe principle. His significance is that it avoids the measurement error of the three-dimensional measuring instrument caused by the error of the guide rail.

2. The principle of minimum deformation to try to minimize the deformation caused by various reasons for the design and manufacture of optical measuring instruments must be considered the basic principles. Then for the operator of optical measuring instruments, as long as the instrument does not violate the operating procedures, the deformation of the relevant components of the instrument is generally consistent with the principle of minimum deformation. In the use of optical measuring instruments, the operator should focus on the following kinds of deformation, such as contact deformation caused by contact force, self-weight deformation, thermal deformation.

3. The principle of the shortest measurement chain three-dimensional measuring instrument measurement information signal for each conversion is known as a link in the measurement chain, due to the measurement of each link in the chain inevitably introduces measurement errors, the more links, the more measurement errors, so in order to ensure the accuracy of the measurement, three-dimensional measuring instrument measurement chain design to strive to achieve the shortest.

4. Principle of closure by the circular indexing of the closure characteristics of the measurement of the principle of closure, if the measurement can meet the conditions of closure, then the sum of its interval error must be zero. Three-dimensional measuring instrument application of the principle of closure not only in the angle measurement so that the total cumulative error of zero, but also create the conditions for self-checking, that is, without any standard apparatus can be realized in its own verification.