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The article is devoted to the description of the requirements for the accuracy of control devices and the development of methods to ensure the claimed dimensional accuracy by methods of dimensional analysis. The conditions for ensuring the accuracy of the assembly scheme, the determination of the dimensional chain and dimensional analysis of the dimensional chain during the assembly of the control device, as well as the main causes of errors during assembly and ways to eliminate them are listed. In addition, the consequences of the influence of irregular gaps in the interfaces of the control device parts on the measurement accuracy are presented, various types of assembly dimensional chains are considered, tasks solved when calculating the dimensional chain. The paper presents a compiled dimensional chain of the technological process of assembling a measuring instrument for monitoring the alignment of the inserts of motor-axial bearings of traction electric motors of locomotives, which represents a dimensional chain of the first type and is a chain with linear dimensions and vertically parallel links. The purpose of the work is to substantiate the calculated tolerances and limit deviations of the links of the assembly dimensional chain, providing the required value of the closing link for the proper functioning of the assembled measuring instrument. The paper describes the selection of the closing link of the dimensional chain, the selection of the links that make up the dimensional chain, the calculation of the limiting deviations of the closing link that ensure the required measurement accuracy during operation of the control device and the calculation of the limiting deviations of the components of the links of the dimensional chain by the "maximum-minimum" method. Thus, the article presents a solution to the design problem of dimensional analysis, which consists in determining the accuracy of the component links of the dimensional chain when assembling the control device according to the known calculated tolerance of the closing link and its limit deviations.