It is shown that when the quantum limitations are starting to affect significantly the accuracy of measurement, the quantum entanglement of the studied system states can be used for the deep active suppression of background noise. The entanglement ensures an "extra degree of freedom" allowing to select the required events and to cull the noise. The examples of such situation are considered.

The new method of integral characteristics measurement based on comparison of input and additional sinusoidal signals instant values is considered. The results of analysis of influence of signals instant values quantization on the parameters measurement error are presented.

The corrected model of determining the capacity of the gas pipeline with taking into account the inertial and gravitational components providing the more correct results is suggested. The model allows to carry out the calculation for horizontal and in lined pipelines.

The analytical expressions establishing the relationship between the aperture uncertainty appearing in the form of random deviations of the measurement signal readout moment and the consequent error of the result of measurement of active power of periodic non-sinusoidal current for normal and uniform probability distributions of the deviation - are obtained. These formulas are obtained for the two measurement methods based on the definition of active power from the measured instantaneous values: 1) voltage and current, 2) current in the active load.