Gossen MetraWatt METRAHIT ENERGY TRMS System Multimeter Operating Instructions Manual page 54

Measurements: V/Hz/dB – PQ/
Harmonic Analysis – Total Harmonic Distortion THD
With 32 sampled values per mains period (16.7; 50; 60 or 400 Hz
can be selected in the menu), harmonic analysis is executed
approximately once per second. FFT (fast Fourier transformation)
makes oscillations up to the 15
These are used to calculate the RMS values of the fundamental
harmonic (HD 1) and the individual higher harmonics (HD 2 ... 15),
as well as total harmonic distortion (THD). RMS values and distor-
tion components are displayed in each case (RMS values relative
to the RMS value of the fundamental harmonic).
Due to the fact that the TRMS system multimeter is not equipped
with a special anti-aliasing filter, existing distortion above the 16
harmonic may influence measurement results for the higher har-
monics.
Parameters for Harmonic Analysis
Ð Before measurement, please select the fundamental mains fre-
quency from the HARM menu with the help of the HARM.F pa-
rameter, namely 16.7, 50, 60 or 400 Hz (50 Hz = default
setting) (see section 6.4, "Entering Parameters – SETUP Menu").
54
– MHz/% – /nS/R
–
SL
th
harmonic available to this end.
/ – Temp – /m – W/Wh – A/Hz/thd
th
GMC-I Messtechnik GmbH