  Accurate measurement of pressure with a wide dynamic range holds significant
importance for various applications. This issue can be realized with a
mechanical nano-oscillator, where the pressure-related collisions with
surrounding molecules induce its energy dissipation. However, this energy
dissipation of the nano-oscillator may be overshadowed by other processes.
Here, we apply the second-order coherence analysis to accurately characterize
those distinct dissipation processes. Based on an optically levitated
nano-oscillator, we successfully obtain precise measurements of the air
pressure surrounding the particles from atmosphere to 7E-6 mbar, over 8 orders
of magnitude. It proves that the mechanical nano-oscillator is an extremely
promising candidate for precision pressure sensing applications. Moreover, the
second-order coherence analysis method on a classical system can pave the way
to characterize the dynamic properties of an oscillator, which will benefit
microscopic thermodynamics, precision measurement, and macroscopic quantum
research.
