Alternatives A quality general-purpose electronics digital multimeter is generally considered adequate for measurements at signal levels greater than 1 mV or 1 μA, or below about 100 MΩ; these values are far from the theoretical limits of sensitivity, and are of considerable interest in some circuit design situations. Other instruments—essentially similar, but with higher sensitivity—are used for accurate measurements of very small or very large quantities. These include nanovoltmeters, electrometers (for very low currents, and voltages with very high source resistance, such as 1 TΩ) and picoammeters. Accessories for more typical multimeters permit some of these measurements, as well. Such measurements are limited by available technology, and ultimately by inherent thermal noise.
Alternatives A quality general-purpose electronics digital multimeter is generally considered adequate for measurements at signal levels greater than 1 mV or 1 μA or below about 100 MΩ; these values are far from the theoretical limits of sensitivity and are of considerable interest in some circuit design situations Other instruments—essentially similar but with higher sensitivity—are used for accurate measurements of very small or very large quantities These include nanovoltmeters electrometers (for very low currents and voltages with very high source resistance such as 1 TΩ) and picoammeters Accessories for more typical multimeters permit some of these measurements as well Such measurements are limited by available technology and ultimately by inherent thermal noise