4. Measuring bridges

As we have just seen, the current generated by today's monoelectronic devices is low, ranging from 10 pA to some 100 pA. The easiest way to measure this current accurately is to compare it with a current whose value is known and traceable. Low-noise ammeters are commercially available, but their gain has a temperature coefficient (several 10 ^-5 /°C) which prevents any current measurement with uncertainties of less than 10 ^-6 . In this section, we propose measurement bridges for metrological study of this monoelectronic current, in order, for example, to study its quantification limits, or to implement the project to close the metrological triangle (see §