The authors discuss problems associated with the improvement of the accuracy of measurement of parameters of pulse and harmonic signals by the histogram method and with the measurement of high-frequency (HF) signal amplitude with the aid of a synchronizer. The following conclusions can be drawn from this study. The error in measuring signal parameters with the aid of a sampling oscilloscope depends on the noise in horizontal and vertical deflection channels. Application of the histogram method gives simple algorithms for measuring certain parameters of pulse and sinusoidal signals and makes it possible to eliminate the effect of the horizontal channel noise on the results of measurement. Vertical deflection channel noise is a source of a systematic error in the measurement of sinusoidal signal amplitude by the histogram method. This error can be calculated and eliminated as proved by experimental measurements carried out with the S9-9 precision sampling oscilloscope.