FIELD: diagnostics of control systems and their units. SUBSTANCE: controlled object is in the form of dynamic unit with transfer function of fixed-structure control system including four dynamic units. Nominal values of evaluated parameters of transfer functions of dynamic units are determined. Then evaluation of the whole system transfer function is performed, and nominal value of transfer function of monitored unit is realized on base of received nominal values of transfer functions of system. Then dynamic unit of control system is monitored by means of exchanging correct circuit by monitored one for determining fluctuation of nominal value of evaluated parameter of transfer function of monitored dynamic unit. Value of that parameter allows to detect if operation of monitored unit is correct or not. Apparatus for performing the method includes driving circuit, test signal source, generator of non-linear function, five multiplication units, three adders, two dividers, amplifier, tolerance control circuit. EFFECT: enlarged functional possibilities of method. 2 cl, 3 dwg
