In-situ measurement of temperature and pressure in fluid films using ultrasound

Measuring and controlling temperature and pressure is of paramount importance to ensure safe and thriving conditions for life, and reliable operation for machines and processes. Conventional measurement techniques are seldom suited to confined environments and tribological contacts. This work aims to enable in-situ measurement of temperature and the pressure of any confined liquid layer. To achieve this, an ultrasonic viscosity measurement device equipped with a matching layer was repurposed. Changes in the operating conditions caused the expansion and compression of the matching layer, in turn causing a time shift of the ultrasonic signal. The temperature range spanned from 20 °C to 60 °C, while pressures were measured from ambient pressure up 600 MPa. It is further proposed that tailoring the material of the matching layer to the expected operating conditions can enhance both the sensitivity and accuracy of the measurements.