Automated impedance metrology extending the quantum toolbox for electricity

Short Name: AIM QuTE, Project Number: SIB53
Power resistors

Impedance measurements for electrical components: Simple, reliable and cost-effective impedance measurements 

Electrical impedance is used in the manufacturing process for electronic components such as resistors and transformers, to analyse touchscreens and fuel gauges, and to calibrate dosimeters for ionising radiation measurement. Impedance is the resistance of an alternating current (AC) electric circuit, and is a measure of the opposition that a circuit presents to the AC when a voltage is applied. An impedance bridge is an instrument used to measure impedance; the units of which are the ohm (), the farad (F) and the henry (H).There are a variety of different types of impedance bridges, and this project looked at two of these – (1) Josephson bridges and (2) automated digital bridges.


Prior to this project, it was only possible to calibrate impedance at certain predefined set values, by comparison with a standard with a known impedance. However, this was an issue for end users and manufacturers, who need to measure impedance at arbitrary values.


This project improved the European capabilities for impedance measurements by developing new standards, methods and traceability routes needed to establish impedance scales at the lowest level of uncertainty (i.e. 10-7 between 10 Hz and 20 kHz). The project developed Josephson and digital impedance bridges capable of calibrating impedance at values ‘in between’ the previously defined set values of impedance standards.

Project website