A novel and compact photoacoustic sensing system to estimate thermophysical properties of the lubricant oil

A novel and compact photoacoustic (PA) sensing system to estimate thermophysical properties of the lubricant oil is presented here. This study simultaneously assesses the viscosity and temperature of the industrial grade lubricant oil. Unlike the conventional PA sensing, which uses high energy pulsed lasers, this study presents a compact, continuous wave (CW) laser diode based sensing system to probe the oil samples; where acoustic interferometry is introduced to enhance measurement sensitivity. Here, the measurements are conducted on the different multigrade lubricant oil (SAE-20W40 & SAE IOW40). Certain novel features are extracted from the time domain PA signal to estimate the viscosity and temperature. The experimental results are found to be statistically consistent and comparable to the theoretical viscosity value for distinct temperatures with less than 8% deviation. It is envisaged that this compact system can be effectively deployed in an industrial environment for in-situ quality inspection of lubricant oil.