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Continuous measurements of deformations of the Earth's crust make it possible to record changes in their character in several characteristic parameters. Such parameters include the amplitude, phase, and frequency of periodic oscillations, for each characteristic frequency separately, as well as random typical or atypical artifacts. All this information with proper processing can be used for various purposes, one of the most important tasks in this case is to reliably identify earthquake precursors. These studies require a preliminary long and detailed record of all measurements, followed by mathematical and statistical processing. In this case, strain measurements are carried out using laser meters that convert the ultra-small increment of the distance between the control points into digital samples. These increments of the distance in the measuring system are initially converted to phase increments of the high-frequency laser radiation, then to the same phase increments of the electrical signal at an intermediate high frequency, then the phase increments are measured using a special device called a phase meter, which generates digital samples of the phase increments proportional to the increments of distances. Phase meters have rather high requirements for the accuracy and speed of measurements; in addition, they must be protected from the influence of deep amplitude modulation on the accuracy of measurements. In any case, these modulations should not be fatal for continuous phase measurement, that is, there should be no loss of measurements during a sharp decrease in the signal amplitude. This paper proposes a new method for continuous high-precision measurement of phase increments using a phase-locked loop(PLL), organized by a fundamentally new principle of operation, namely: similar to the operation of a sigma-delta analog to digital converter(ADC). This type of ADCs uses auto-tuning of the output signal to the input in a circuit containing only an integrator and a comparator, as a result of which high-frequency transients in the form of fast self-oscillations near the equilibrium state constantly occur in this loop. The advantage of this method allows measuring of the low-frequency component of the input signal with extremely high accuracy. [ABSTRACT FROM AUTHOR]