Coriolis mass flowmeters (CMF) are claimed to be not affected by the properties of the liquid such as heat conductivity, heat capacity and viscosity. They are direct mass flowmeters and form a real mean along the flow profile. However, there is some evidence from field applications that the devices, in particular with single straight pipe, suffer under the null drift. Therefore, the zero shift must be adjusted to the properties of liquid, installation site and operating conditions. The zero shift is caused by asymmetry of the oscillating system. A change in the asymmetry leads to the zero shift. This paper presents two methods to determine the zero shift: a sensor and a model based approach. The first uses additional acceleration sensors to measure the vibration of the straight pipe’s mounting. The motion of the mounting represents asymmetries in dissipation. The second method utilizes a model which includes the asymmetries as parameters. These can be detected by auxiliary exitation of the oscillating system.

Cavitation is in most cases harmful and undesired phenomenon in fluid power systems. When actions for preventing cavitation are considered, it is essential to recognise the existence of cavitation and location of cavitation inception point. In fluid power components and systems cavitation can occur in various locations where the access for measuring instruments is limited. Therefore, the existence of cavitation is often very difficult to detect. In addition, very high speed of the cavitation phenomenon makes the task difficult.
At the Institute of Hydraulics and Automation several cavitation detection methods have been studied. The existence of cavitation can be detected either directly or indirectly. Indirect detection can be done by monitoring steady-state flow properties and with high-speed pressure transducers or accelerometers the cavitation-induced shock waves can be recorded. Measurement of frequency spectrum of acoustic pressure reveals also the presence of cavitation. When flow visualisation is possible to arrange, cavitating flow can be observed directly. In addition, an ultrasonic transmitter-receiver has been tested for direct cavitation detection.
The above-mentioned equipment has been used in several cavitation studies at the IHA and promising results have been obtained.

Designing bluff-bodies for the ultrasonic vortex frequency measurement almost leads to very different geometries as they are used for the vortex detection method by pressure sensors. In some cases they have the same form but they are facing their backside to the inflow. The developing process is not only restricted by the demand for a constant Strouhal number and a strong linear dependency of the vortex frequency to the mean flow velocity but also by the vortex detection method.

This paper illustrates the design and the development of a thick-film mass flow sensor based on the frequency shift of a resonating ceramic structure. The mechanical oscillator realized uses a measurement principle of thermoanemometric type. The sensor can measure mass flows up to 15 × 10⁴ sccm (sccm: 10 sccm = 0.17 mg/s), with high sensitivity. Here we report on the first prototype consisting of a beam 0.254 mm thick , 4 mm large and 17 mm long, in which the temperature variations induced by flow, affect the resonance frequency. Predicted and measured values for the shift of the resonance frequency agree well. At the first flexural mode of vibration of 3.5 kHz and at an average temperature rise of the substrate of 100 ° C, a frequency change of 500 Hz in the mass flow range from zero to 15 × 10⁴ sccm can be measured. Indications are proposed for reducing the time response and increasing the sensitivity.

This paper is concerned on the new type of the sensing elements for a particle volume of flow rate measurements based on cross correlation flowmeters. The new type of sensing elements exploit the fact that the solid particles being carried by a flowing air and impacting a properly formed obstacle generate an acoustic surface wave (acoustic emission - AE). The acoustic signal is indicated by the aid of a high sensitive transducer, which converts the acoustic signal to an electric one. If we use two sensing elements in the flow channel with defined distance, we may use cross correlation technique for calculating transit time and then from time and distance of obstacles the speed of particles.