Research on a Rapid and Portable Measurement Method of Oil Density Based on Asynchronous Free Resonance

In response to the demand for rapid and portable measurement of oil density, this article establishes a full‐period vibration model including the transient excitation stage and the free attenuation stage based on the fluid inertia effect and viscous dissipation effect. The entire process characteristics of oil vibration are fully utilized, and the analytical equations among density, resonant frequency, attenuation rate, and temperature are derived. In terms of structural design, it has broken through the traditional symmetrical structure and innovatively proposed a double‐curvature S‐type asymmetric resonant tube structure. By integrating the transceiver integrated transducer system, the spatiotemporal separation of the excitation signal and the detection signal has been successfully achieved. This method not only improves the signal‐to‐noise ratio but also reduces the system complexity and minimizes the system volume, thereby expanding its application scope. Experimental verification shows that the measurement accuracy of this system in standard solutions (25°C) reaches ±0.00064 g/cm 3 . Repeated tests on typical oil show that the average error is 7 × 10 −4 /cm 3 , and the measurement standard deviation is less than 5.8 × 10 −4 . The effectiveness of the density measurement system was verified.