Development of an ultrasonic sensor system for determining the concentration of dissolved substances in liquid dispersions

ISAT subproject: Multisensor concept and evaluation algorithms

Ultrasound (US) has been used for analytical and diagnostic purposes for decades, for example for non-contact level measurement or sonography in the medical field. US is also frequently used for process monitoring in plants that process liquids, such as in the beverage or chemical industries, for example, for flow or gas bubble detection. The major advantage here is that US can penetrate even opaque media, such as milk, and is therefore also suitable for applications where optical measurement systems fail.

The numerous interactions between ultrasound and the medium through which it passes allow conclusions to be drawn about the composition of a homogeneous or heterogeneous mixture of substances. In fluid-carrying systems, ultrasonic sensors are therefore used for flow measurement, concentration measurement of dissolved substances, or the detection of dispersed phases such as particles, droplets, or, in particular, gas bubbles. A current challenge remains the concentration measurement of dissolved substances, e.g., sugar, in the presence of dispersed phases. The reason for this is that such dispersed phases strongly scatter the sound. Reliable transit time measurement—i.e., measurement of the sound velocity, whose change is used to determine concentration—is then difficult or even impossible, as the detector does not receive a sufficiently high signal amplitude or is overwhelmed by interference signals. Another challenge is posed by deposits on the sensor, which often build up gradually during a production cycle. These deposits typically result in a different sound velocity and thus a signal drift in the transit time.

The goal of this project is to develop an ultrasonic (US) sensor that can reliably determine the concentration of dissolved substances in dispersions despite interference from air bubbles, particles, and deposits on the sensor. To this end, a multisensor system is to be designed that is capable of reducing interference signals by varying the US signals in terms of frequency, amplitude, and modulation, while simultaneously characterizing the medium under investigation using suitable algorithms to reliably determine the concentration of dissolved substances within it despite interfering influences. A key aspect of signal evaluation is that the algorithm must be able to distinguish between a measurement disturbance caused by dispersed phases and a deviation in the monitored production process that leads to non-compliance with the setpoint. A genuine process deviation, in contrast to a measurement disturbance, can result in significant economic damage due to plant downtime or scrap. Consequently, a clear metrological distinction between disturbance and process deviation is essential for continued plant operation and product quality.

Funding Agency: Startseite – BMFTR

Funding Program

KMU-innovativ: Production Research, Theme Area “Future of Value Creation”

Project Title

Development of an Ultrasonic Sensor System for Determining the Concentration of Dissolved Substances in Liquid Dispersions (konDispUS)

Duration

January 1, 2024 – June 30, 2026

Funding Reference Number

02P23K041

ISAT Funding Amount

€249,892