The Requirements for Determining the Pair-radius Correction of the Circle

Some information about the circle, the reading microscopes and the corresponding reading system of the LLMC is given in this paper. The necessity to determine each pair-radius correction is expounded from the angle of the classification of the circle division error.It is analyzed from the composition of the error contained in the circle reading that the influence of the circle pair-radius division error, the installation error between the circle and the reading microscopes could be determined together to correct the circle reading by using the method of fixing the angular distance, i.e., the relative position between the reading microscopes and the circle is kept as constant in the course of determining correction, observing and reading on the condition that no strict requirements are set on the assembly of the circle and reading microscopes.