Ultrasonic density sensor for liquids

This paper presents a new ultrasonic density sensor for liquids. It unifies high accuracy with high durability and is suitable for a wide range of tube diameters. The sensor comprises a transducer consisting of a piezoceramic disk mounted between two reference rods of quartz glass. Additionally, a second transducer is used as a sound receiver. The density is obtained from the reflection coefficient of ultrasound at the interface between the quartz glass rod and the liquid, and the transit time of sound between this interface and the second transducer. Parameters like a high long term stability and accuracy of ±0.2% were achieved by an internal acoustic reference measurement and a high signal-to-noise ratio. The latter was gained by using the sound radiated from the rear side of the piezoceramic disk as the reference. Advantages of the new sensor are discussed and experimental results are given. Applications of the sensor comprise concentration measurement and ultrasonic mass flow measurement