What physical principle do modern Proton Precession Magnetometers (PPMs) utilize for their accuracy?

Answer

Nuclear Magnetic Resonance (NMR) frequency of protons

The PPM achieves high accuracy, sometimes up to 1 ppm, by relying on the precise, inherent frequency derived from the nuclear magnetic resonance of protons.

What physical principle do modern Proton Precession Magnetometers (PPMs) utilize for their accuracy?
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