Automation of an ultrasound velocity measurement system in high-pressure liquids

A system for the measurement of ultrasound velocity in liquids was automated to cope with variations in temperature (293.15 K less than or equal to T less than or equal to 373.15 K) and pressure (P less than or equal to 100 MPa). The following problems had to be solved: supervision and monitoring of the achievement of the required pressure and temperature, creation and reception of the signal, acquisition of the measurement points, identification of the signal received on the basis of the characteristics of a reference signal, measurement of ultrasound travel times, memorization and processing of the results. The system enables substantial savings of time compared with manual methods. The system calibration procedure is also described. Measurements of octane and pentane (which had been studied previously) are used to verify the validity of the system developed and to determine its degree of accuracy (absolute average deviation from literature data 0.1% and maximum deviation from literature data 0.25%).