Water content measurement in granular materials using ultrasonic waves

The measurement of the water content of granular materials is an important task in agriculture as well as in the food industry. No available measuring method provides completely satisfactory results either because of the lengthy measurement operations or due to the maintenance of accuracy problems. This paper discusses the possibility of determining the water potential, from which the water content can eventually be determined, by using ultrasonic waves. The discussed solution employs the ultrasonic waves to determine the velocity of sound in a chamber inserted into the material and a solid state sensor to determine the temperature. The knowledge of these parameters allows one to compute the relative humidity from which the water potential is readily obtained. Experimental results are reported that refer to tests carried out in a soil sample under controlled conditions and that confirms the feasibility of the solution.