A special and often overlooked property of materials is electrical conductivity. It is based on a material's ability to conduct an electrical field and serves as a unique fingerprint of a material or mixture of materials in a given state. The conductivity is particularly influenced by the temperature and frequency of the electric field. The mathematical reciprocal of conductivity is electrical resistance, known as impedance when considering its frequency dependence.

Understanding impedance is crucial when it comes to characterizing material mixtures. In this context, electrical impedance spectroscopy (EIS) refers to the process of measuring impedance over a wide frequency spectrum, while electrical impedance tomography (EIT) involves determining spatial impedance distribution. These are two powerful techniques that play a key role in the analysis and characterization of material mixtures.

EIS allows for the examination of the electrical properties of a material mixture across a broad frequency range. This provides the capability to determine the composition and distribution of components within a mixture. Since different materials exhibit different impedances, EIS can provide information about the nature and concentration of materials present in a mixture. This is especially valuable in the fields of material science, chemical analysis, and quality control. Inferring individual components within a material mixture requires a system understanding, which can be achieved through targeted modeling or machine learning.

On the other hand, EIT enables the spatial imaging of the electrical properties of a material mixture. It can be used to visualize the distribution of materials within a container or structure. By measuring impedances between various electrodes within the same volume, a 2D or 3D image can be computed through mathematical reconstruction. Various techniques such as tomographic methods, FEM-based approaches, or machine learning-based approaches can be employed. This is essential in medical imaging for tissue and organ diagnostics and in process industries for monitoring mixing processes.

A common method for impedance measurement involves simultaneously measuring current and voltage during the electrical excitation of the system, which can be achieved using current or voltage sources. To meet the diverse requirements of materials and electrode combinations, application-specific circuit development is necessary.

Our Equipment:

• Established impedance measurement systems
• Custom-designed impedance measurement circuits
• Frequency generators
• Oscilloscopes