摘要 : Standards maintenance is made by repeated measurements over long periods of time. In the presence of divergent low-frequency noise, the longer the observation time, the greater the measurement uncertainty. Long-term fluctuations a... 展开 Standards maintenance is made by repeated measurements over long periods of time. In the presence of divergent low-frequency noise, the longer the observation time, the greater the measurement uncertainty. Long-term fluctuations associated with standard resistors, voltage standard cells. standard weights, and the measuring equipment used are discussed. Groups of these standards are periodically compared at definite time intervals. Spectrum signal analysis is carried out by discrete Fourier transformation, showing in some cases 1/f/sup n/ power spectra with different values of n. 收起