User manual

39
Subject to change without notice
Q u i c k i n t r o d u c t i o n Q u i c k i n t r o d u c t i o n
Activate the marker by pressing the soft key DISPLAY. The se-
cond marker will now appear in the center of the display. Select
the marker by pressing the soft key POSITION (the marker
indication will turn to orange) and move it with the knob (to the
right) or via the keyboard by directly entering the value 200 MHz.
Fig. 3.4: Measurement of the harmonic of a sine wave signal
3.3.1Selectionoftheproperltersettings
In order to better resolve the harmonic from the noise, the RBW
andtheVBWltersshouldbeadaptedtothemeasurementtask
by using the bandwidth menu (key BANDW
9
). The HMS series
standard procedure is to automatically set the RBW and VBW
lterssuchthatarstapproximationofameasurementofthe
inputsignalwillbepossible.Manualselectionofthelterswill
be always superior to an automatic presetting.
Activate the key BANDW
9
to enter the lter menu of the
spectrum analyzer. Due to the presettings, the RBW and the
VBW will be set to AUTO. Activate manual setting by pressing
thetopsoftkey,thenusetheknobtoselectthe100kHzlter
from the list in the menu which will appear.
The noise band displayed formerly should now be markedly
reducedsuchthattherstharmonicwillbe bettervisible.
A further reduction of the RBW would display the harmonic
still better at the expense of a massively extended sweep
time. Here, a compromise must be found between display
quality and measurement time, optimum for the actual mea-
surement task.
Fig.3.5:Selectionoftheproperltersettings
Another means of spectrum analysis is the socalled video
bandwidth (VBW). This is nothing else but a lowpasslterwhich
ltershighfrequencycomponentsfromthesignal.Usingthis
ltercanalsocauseamassiveincreaseofthesweep time, and
again a sound compromise has to be found between display
quality and measurement time.
Activate the manual VBW selection by pressing the associated
softkeyandusetheknobtoselecta10kHzlterfromthelist
in the menu which will appear.
Both levels (fundamental and harmonic) should now be well
visible on the HMS display.
3.3.2 How to measure the harmonic
In chapter 3.3.1 already two markers were positioned on the
fundamental and the harmonic, the second one on the harmonic.
Open the marker menu by pressing the key MARKER
15
.
The marker [2] is still selected (shown as an entry on the top
soft key) Change the active marker [2] from an „absolute“
marker to a „relative“ DELTA marker by pressing the soft
key DELTA. The marker display will change from an absolute
frequency and level display to a relative frequency and level
display; the values shown refer always to the main marker
(marker [1]).
Fig. 3.6: Measuremen of the harmonic using the delta marker
3.3.3 Extended marker functions (PEAK SEARCH)
Press the key PEAK SEARCH in order to reach the extended
marker functions. Select the marker to be used with the key
(MARKER >
14
). In the top screen area (where the level and
frequency values of the markers can be read) the lettering of
the marker selected will be shown pronounced bright.
Select the marker [2] and press the soft menu key PEAK. The
second marker should now jump to the same spot where mar-
ker [1] already resides (that is the position of the fundamental),
because the level of this is the highest. The values displayed
for (DELTA-) frequency and level should be „0“.
Press the soft menu key NEXT PEAK in order to cause the ac-
tivemarkertopositionagainontherstharmonic.Thevalues
displayed for (DELTA-) frequency and level should be identical
to the original ones.