## 1 Introduction  
The assessment of the quality of insulation materials is of significant importance in modern technology. It is very important, for example, in the energy industry and automotive technology. The quality of insulation determines the trouble-free operation of electrical installations and devices, as well as the safety of their use, which is very important [1, 2, 3]. Various indicators are used to assess the quality of electrical insulation materials. One of them is the dielectric loss factor tan \(\delta\). The dielectric loss factor is a relative quantity defined for real capacitors filled with dielectric material, and an insulating system can generally be treated in this way. This coefficient is determined as the ratio of the power losses in the tested capacitor to the power stored in it. In typical electrical insulation systems, values from \(10^{-1}\) to \(10^{-5}\) are required, which means that power losses in insulation are range from fractions of a percent to as much as 10%. In assessments of the quality of insulation, the value of the dielectric loss coefficient itself is less important; the changes in this coefficient are more important, indicating the degradation in insulation of the tested device or installation. In the measurement of the dielectric loss factor, high requirements for measurement accuracy are not set. It can be seen that the dielectric loss factor is the tangent of a certain phase angle, by which the phase shift angle between the voltage and current of the tested capacitor decreases due to the flow of the active component of the current through it. For this reason, the dielectric loss factor is often referred to as tan \(\delta\). Analog and digital measurement methods are used to measure \(\tan\delta\). Its value is also a relation of the corresponding impedance components [4; 5; 6; 7; 8; 9]. Measurement circuits require the tested object to be supplied with a voltage or sinusoidal current. The measurement signals are the voltage and current of the object being tested. These signals are generally processed in non-zero or zero measurement circuits. In non-zero circuits, the output non-zero signal of the circuit is a function of the measured parameters, while in zero circuits, the circuit is driven to the equilibrium state, which usually means reaching the zero value of the selected signal, and then the values of the measured quantities are determined on the basis of the parameters of the measurement circuit. An example of such circuits are balanced bridge circuits [4; 5; 6; 7]. Bridges and other zero systems can measure \(\tan\delta\) directly. One of the most popular bridge circuits, designed to directly measure the dielectric loss factor, is the Schering bridge [4; 5]. The power relation defining \(\tan\delta\) can also indirectly be determined as an impedance component relation. Bridges are also being built, in which some of the bridge elements are replaced with digital elements. Such bridges are called digital bridges [10; 11; 12; 13; 14; 15; 16]. In all cases of zero methods, the problem is the so-called bridge's convergence. It is the result of the bridge balancing process, which minimizes the output signal by means of successive alternating settings of the control elements. This process can be long-lasting and sometimes completely prevent the bridge from being balanced. Measurement circuits often use the digital processing of measurement signals to measure impedance components [8; 9; 10; 11; 12; 13; 14]. Signal processing is sometimes carried out in the form of electronic circuits and in the form of a software chain of measurement signal processing. The measurement algorithm performs operations that are equivalent to electrical connections between blocks of measurement circuits. Such implementations are called virtual instruments. For the design of virtual instruments, software packages can be used, which significantly facilitate modeling, simulations, and, finally, testing of the measurement circuit [17].