Introduction. The main problem of all product condition monitoring systems is the untimely determination of the moment of their contact and the determination of measurement errors. Now problems of surface quality control, measurements of current geometric parameters must be solved at the stage of production preparation when choosing the metrological support of the technological process. Therefore, we can identify the main disadvantages that relate to the currently known methods and devices for determining the parameters of forming the detail, in particular in the presence of a complex shape and internal surfaces, such as holes. First, it is clear that a contact measuring tool can degrade of the precision detail's surface. Secondly, studies have shown that all the described methods and devices work only to control and measure the parameters of the outer detail's surfaces.Main part. Therefore, it is an interesting task to control the quality of internal detail's surfaces, for example, holes. In this case, the task becomes more complicated, due to the instrumental features of registration of the current parameters of detail's shaping.Therefore, it is necessary to consider a model for determining the error's distribution at process of control details. If we have the presence of waviness, surface roughness, or other deviations of submicrogeometry, this leads to the phenomenon of scattering of incident radiation and ultimately affects the actual reflectivity.These dependences need to be considered at creation of devices of control and measurements of parameters of forming of a detail's surface. So, for example, thus, it is possible to offer the device of the control of a condition of internal surfaces of a detail which contains the scheme of a fiber-optic three-channel meter.In addition, if you use radiation sources with different wavelengths, you can get different values of intensities, taking into account the radiation parameters recorded by the photodetector modules, and at the same time get greater accuracy by comparing these values and determining the measurement error.Conclusions. Thus, taking into account the proposed method for determining the surface roughness of the part, it is possible to determine the roughness by the intensity of the light flux reflected from the surface. The surface absorption by mass of the technological object is taken into account, then the degree of height of the rough surface introduces a coefficient that determines the roughness parameters. This takes into account the time required for processing, i.e., which takes into account the dynamics of both manufacturing and changes occurring on the surface of a technological object, which is controlled.