This paper describes a new primary standard at LNE for precision measurement of RMS values and total harmonic distortion of periodic signals containing a fundamental frequency at 50 Hz and quasistationary harmonics which maximum order is 50. The method is based on the sampling of the signals and the analysis of the samples by discrete Fourier transform. The traceability to the SI units is ensured by comparing the measurements to those obtained using a thermal converter. The standard uncertainty for RMS value and total harmonic distortion are respectively 22 µV/V and 0,0025% for all the signals studied.

Key words

primary standard
quasi-stationnary harmonic
sampling technique
aperture time
thermal converter