Up-to-date electrometer tube amplifiers are a perfect equipment for measuring currents and voltages from sources with a large internal resistance, and they can be used for solving a wide range of problems related to electrometric measurements. The current sensitivity of mass-produced tube electrometers amounts to 10−15−10−14 A. Several problems, such as obtaining a logarithmic scale and high-speed systems for measuring very small currents are best solved by means of tube electrometers. It is true that in recent years tube electrometers have acquired an important rival consisting of electrometers with field-effect transducers; however, the latter are as yet in the development stage and one can expect that tube electrometers will for a long time occupy the leading position among other systems used for similar purposes.