This article is about:
- Short explanation how to view a Harmonic in spectrum mode of a ScopeMeter
What are harmonics :
A harmonic is a signal or wave whose frequency is an integral (whole-number) multiple of the frequency of some reference signal or wave.
Harmonics are created by electronic equipment with nonlinear loads drawing in current in abrupt short pulses.
The short pulses cause distorted current waveforms, which in turn cause harmonic currents to flow back into other parts of the power system.
How can I view harmonics with a scopemeter ?
Some scopemeters have the option for spectrum view, this is basically a fast fourier transformation so amplitudes are organized by its respective frequency.
The Fluke-190-II series can display harmonics from bandwith of 1 KHz up to 10 MHz.
So this function is partially usable, only for higher harmonics as of the 20th harmonics in case of 50Hz systems.
Below is an example of a 50Hz square wave form with harmonics in the very high region.
To enter spectrum mode press Scope and then function waveform options, then choose mathematics, and then Spectrum.
Source 1 is set to channel A.
If you want to view a certain harmonic in this view , for instance the one in the middle of 10 KHz to 100 KHz (see above blue arrow), press zoom.
Up/down controls the level of zoom (2,5x or 5x), left/right the view if the frequency range.
Set zoom at and with the left right arrows go to the range from 1KHz to 100 KHz:
Press cursor and the cursor will appear somewhere in screen :
With left/right arrows you now can control the position of the arrow.
Move it to the intended needle you like to know the specific frequency of.
When you have the frequency (fn) and to know if it is a component of the basic frequency (f1) :
The frequencies of the various harmonics are multiples (n) of the frequency of the first harmonic.
Each harmonic frequency (fn) is given by the equation fn = n • f1 where n is the harmonic number and f1 is the frequency of the first harmonic.
So in this case calculate n = fn/f1