Applies to amplifiers used in nuclear instruments to measure very light currents, ranging from about 10-6 A to 10-14 A, as produced e.g. by very high impedance sources such as ionization chambers. Defines the characteristic terms used for expressing the functional performance of d.c. amplifiers and the test methods recommended for measuring and verifying such characteristics. This standard is not intended to imply that all the tests described are mandatory, but only that such tests as are carried out shall be performed in accordance with the procedures given herein. It was deemed that the scope should be as general as possible, and therefore this standard does not distinguish between prototype, type or acceptance tests, nor give numerical values for the various characteristics specified.