Back to our example: the individual vehices are called applications and have
handy abbreviations: for instance, the application “traction power“ has its own
frequency range of 16.7Hz.
We will also replace the formerly used expression “speed“ with something else:
field strength.
So far we are done with all the physical units and wording. Next, spectrum ana-
lysis itself; it works exactly like our motorway:
Say our spectrum analyser should measure all frequency ranges from 0Hz to
400Hz (in our metaphor, the 400m range of the giant motorway). It will step by
step measure each frequency range individually. Starting at 0-1Hz, then 1-2Hz
and so on, until it reaches 400Hz. It will also exactly record the signal strength
in each frequency range, also providing us with the signal strength in each of
the frequency ranges.
Some practical examples:
Let’s assume we want to accurately study the frequency range from 0Hz to
400Hz, and let’s further assume that the following 3 applications are currently
active in this range, with varying signal levels (in practice, you will often find a
far bigger number of applications):
Frequency range [MHz] Application Measurement
16.7Hz Traction power 40
50Hz Mains power 20
350-360Hz Unknown 80
How could such a result be displayed optimally on a measurement device? Well,
first of all, we apply the frequency range of 0Hz to 400Hz on the X axis, from left
to right:
OK, now that was simple. Now, we tag each of the 3 applications on the X axis,
according to their frequencies, and their positions in the frequency range beco-
me visible:
0Hz
400Hz
Firmware V 1.0 / © 2005-2013 by Aaronia AG, D-54597 Euscheid, www.aaronia.com
59
19.0 Spectrum analysis basics
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