Electric current measurements

This article covers the main aspects of electric current measurement: the measurand, measuring instruments, current transducers, and measurement methods that ensure traceability to the International System of Units.

The choice of equipment to be used, as well as that of the most appropriate method, are determined by the type of measurement to be carried out, and by the intended use of the information thus obtained. In fact, the approach differs according to whether the measurements are required for functional tests or to check compliance with a specification or standard, for laboratory measurements, for one-off or repetitive measurements carried out on an automated test bench, or for measurements of high currents or low current intensities, carried out in continuous mode, at low frequency or at higher frequency.

In the case of alternating currents, the quantity to be measured (RMS value, mean value after rectification, etc.) is also a decisive factor in the choice of device, especially when dealing with distorted signals. A description of the parameters that can be measured and the problems associated with signal shape are covered in chapter 1 .

The instrument used to measure electric current is an ammeter. The 2 chapter of this article describes the main types of ammeters, as well as other methods of current measurement. A great deal of emphasis is placed on digital instruments, which, as a result of unceasing progress in the field of electronics, have taken over the market from analog devices. Indeed, the performance of the components and systems on which they are built, the possibility of sampling the signal, enabling mathematical analysis of it and thus giving access to all its characteristics, their robustness and increasingly attractive price, have made their use almost universal.

From a few tens of amperes upwards, current...