The article discusses the errors of the electronic measuring apparatus built at AFIT using the FAM-C and FDM-A methods, dedicated to monitoring the technical condition of aircraft power units. The basic components and variants of the use of the built electronic apparatus are presented: the optimization of the selection of construction parameters and the change of the error level in the selection of various types of construction of a given system. The influence of external factors on errors of the measuring system was also described, including changes in the amplitude of the electrical power generator output signal and the influence of the carrier frequency depending on the phase configuration of the measuring system. The method of comprehensive checking of electronic measuring equipment for FAM-C and FDM-A methods in laboratory conditions was presented.