A Portable Sensor Device for Real-Time Viscosity Measurement of Lubricating Oil

The viscosity of lubricating oil is a critical indicator for assessing both its performance and degradation, and it plays a vital role in the monitoring of equipment condition. To meet the need for portable and automated viscosity measurement of lubricant oil in engineering applications, this paper presents a novel device based on Newton’s law of viscosity and strain-based sensing principles. The device detects the minute deflection of a cantilever beam under fluid impact and converts the induced strain into an electrical signal via bonded strain gauges to measure viscosity. Then, a finite element simulation was performed to optimise the structure of the cantilever beam and determine the placement of the strain gauges. Experimental validation using glycerol-water mixtures and 4050 lubricating oil demonstrated that the device exhibited a strong linear correlation between its output and reference viscosity values, and that it maintained high measurement accuracy and strong applicability under critical temperature conditions, such as the ISO standard temperature of 40 °C, as well as in high-viscosity regimes. Finally, the comparison between the proposed device and the representative commercial products indicated that the device is well suited for on-site industrial viscosity measurement requiring portability, automation, and cost-effectiveness. This work provides a technical reference and practical foundation for viscosity measurement in engineering applications.