The measurement of electrical impedance
Paragrafo

COURSE HOLDER
Luca Callegaro

COURSE DESCRIPTION
The interest in the accurate measurement of electrical impedance is shared by scientists and engineers from different backgrounds. Impedance measurements can be performed on an impedance standard to perform a calibration and issue a calibration certificate. Electromechanical appliances and electronic components can be characterized by impedance measurement to identify the parameters of their equivalent electrical model. Properties such as resistivity, permittivity, and permeability of material samples can be derived from impedance measurements conducted with proper electrical fixtures. Biological quantities related to a tissue, or even to a living being, can be related to their impedance. Sensors of many physical quantities can have electrical impedance as their output. Impedance spectroscopy permits following the evolution of an ongoing electrochemical reaction; impedance tomography is an imaging technique.
When performing an impedance measurement, the experimenter faces conceptual and practical difficulties, which are not encountered in resistance measurements. Voltages and currents become geometry-dependent quantities, and different parts of the measurement circuit can interact in unexpected ways because of mutual capacitances and inductances. Even commercial impedance meters ask for careful wiring techniques, which may involve a number of conductors. The measurement result can be expressed in a variety of representations, related to non-trivial mathematical transformations, which are prone to be misinterpreted.
The course will focus on the physical definition of the quantities related to impedance, and their representation; the materials and methods of impedance measurements; the applications of electrical impedance measurements; the metrology of electrical impedance.

COURSE TOPICS
- Main definitions of the quantities related to impedance; theorems; impedance representations
- Impedance definitions
- Devices, appliances, circuits, and instruments employed as building blocks of impedance measurement setups
- Main impedance measurement methods
- Application of mixed-signal electronics in impedance measurement
- Measurement of electromagnetic properties of materials; sensors for non-electrical quantities
- Primary impedance metrology
- Realization of impedance units in the SI

HOURS
10

FREQUENCY
Biennial

TEACHING PERIOD
Spring

LEVEL
Advanced

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