## 1 Introduction
In addition, it is necessary to simultaneously solve the problem of not only obtaining actual results but also to assess the impact of transients during the receiving of a new self-oscillating \"product-stand\" mode. This is a multi-parameter problem wherein various methods are used to solve, including reducing the dynamic effect of rotation elements (rotors) [15; 16] or due to the think selection of turbine block blades [17] or integrated approaches [18; 19]. However, insufficient attention is being paid to the influence of frequency interactions with measurement elements embedded in the stand's equipment since frequency interaction can lead to incorrect results of measuring the output parameters of the equipment under test at the stand. In this case, it is necessary to study the eigenfrequencies and forced frequencies of the elements of the stand's equipment, both with the tested product and without it. To control the vibration parameters, various means and devices and various methods for processing vibration signals are offered. Equally important is the identification of the causes leading to a change in the error of the attorney measuring devices during stand tests of various mechanical systems [9; 20]. This is especially important for units that provide a minimum dispersion of traction characteristics of various power plants; therefore, strict requirements are imposed on them to meet the specified power characteristics. Therefore, measuring the actual power of the turbine of a turbopump unit depending on the speed (number of rotations) of the turbine allows us to build processes for regulating the operation of the power plant; thereby, minimizing losses (an increase in the error in measuring the power of the turbine is the additional mass of fuel for the gas generator to work). There are quite a lot of works on the actual change in the error when changing the number of rotations [21], which allows us to take into account when developing the power unit operation algorithm both when entering the mode and in control problems during stand tests of the turbine. Stand tests of turbines usually have an electric drive part, which provides loading of the turbine during its tests as part of the stand. Typically, this is a generator with a speed reduction system (multiplier), which is mounted on the same frame with elements for measuring the speed of the turbine and its torque. Consequently, the presence of certain structural elements can be based on the works [5; 7]. It can be assumed that these elements of the stand will affect the dynamic behavior of the stand during turbine tests. Figure 1 shows a part of the installation of the stand with a generator and a multiplier, indicating the points of measurement of the level of vibration during testing and the study of the modal characteristics of these elements mounted on a common frame of the stand. When testing the elements of mechanical systems, there is a significant impact on their operation. It is important to understand the influence of the stand's elements on the measurement results. In this paper, we do not evaluate the errors of the measuring system, but we pose the problem of identifying the discrepancy between the expected value of the turbine power at certain numbers of its rotations (calculated value) and its measured value during testing in the stand. Nowadays, there are practically no studies aimed at obtaining the influence of the stand's equipment on the stand's measuring systems. For example, when a turbine block at the stand is working, a significant spread in the magnitude of the realized torque with its calculated value was revealed. This is especially observed during transients associated with a change in the turbine operating modes. In addition, during the steady-state process, at certain rotations of the turbine, oscillations of the measured torque in time relative to its average value are recorded.