Acoustic Sensors

The extraction of information from acoustic waves is the focus of the research on application of acoustic sensors. This can be accomplished by analysis of a passive acoustic spectrum emitted by an observed process. The monitoring or condition monitoring of vibrating parts, devices or systems is often of central interest. Insight into physical properties e.g., material flows, levels or media compositions can be gained from the interaction of waves inherent within a process.

In Addition, several activities in the field of solid-borne sound analysis and simulation with finite element methods (FEM) and modeling of characteristic sound propagation phenomena benefit from experience gained in transducer development.

The in-line analysis of liquid systems puts special demands on measurement techniques in terms of media, temperature and pressure resistance.  This limits the number of measurement principals that can be implemented in device technology and often requiring application-specific solutions. One such example is the combination of an acoustic and dielectric measurement in one sensor, the SoniCap that allows the monitoring of the speed of sound, the sound attenuation and electric conductivity or permittivity on a laboratory scale.

Application-specific measurement devices usually require specialized electronics for sensor signal generation, capture and evaluation. This includes e. g. research on coded excitation signals, various multi-channel multiplexing techniques and special broadband amplifier design.

Micro-resonant sensors as primary mass-sensitive devices can be applied as chemical or biological sensors for gas or liquid phase processes. Their resonance frequencies have a sensing resolution in the order of nanograms. Usually the QMB- (quartz micro balance) or LFE- (lateral field excitation) sensors are built from quartz crystals. Those sensor elements are sensitive to thin coating layers of the material under test. Special oscillators, various types of measuring cells and acquisition equipment are available as a result of many years of R & D activities in this field.