In a resonator circuit, when applying a voltage, the phase difference between the voltage and current will vary depending on the frequency of the voltage source.

How do I physically measure the phase difference between the input and output of the resonator circuit with a high degree of accuracy?

Could we also measure the frequency somehow? I know that

frequency = phase/time

therefore, Δf = Δphase /Δtime.

So, in practical applications, does this mean I would find the difference in frequency of the two signals and multiply by the time frame?

Thank you in advance.