Low-frequency spectral analysis of DC nanovoltmeters and voltage reference standards

Low-frequency spectral analysis was carried out with a personal computer. The method was used to determine the bandwidths of dc nanovoltmeters and provide clear interpretations of the filter and statistical functions in these instruments. Once characterized, nanovoltmeters were used to study the noise characteristics of standard cells and Zener diode reference standards. The spectra led to the discovery of a temperature dependence in the output voltage of some Zener standards.