Do you like however to perform a very accurate level measurement, you should
not set the filter bandwidth too narrow, as very narrow filters can, due to
the inherent phase noise, display levels lower than actually present.
For example, consider measurement of a signal at 100kHz, using a 10kHz filter.
Changing to a 3kHz or 1kHz filter might not cause any significant change in
the displayed level. However, at some point, for example with the 300Hz or
100Hz filter, the displayed signal level will suddenly drop slightly, thereby
delivering an incorrect readout due to phase noise.
8.4 Choosing the right Sampletime (SpTime)
If you want to measure levels it is
very important
to choose the right sampleti-
me. If you use a to small sampletime you can get to low level results. Especially
if you use low filter (RBWs) you have to set the sampletime quite high (depen-
ding on filter even up to a view seconds).
The right sampletime depends on the used Filter (RBW). You should set the fol-
lowing RBWs and sampletime:
10Hz=70s, 30Hz=30s, 100Hz=7s, 300Hz=3s, 1kHz=700ms
etc.
If the Span is bigger then 20 times the RBW you must use a higher sampletime!
Please note that the sampletime in DFT mode (1Hz and 3Hz filter) is limited
to 5s.
A too small sampletime in DFT mode is easy to detect: The levels will fre-
quently change a lot after each sweep. If you use our free PC-Software you will
then see a “snake like” graph in the spectrogram window. Simply change the
sampletime to a higher value until you get a stable reading after each sweep.
8.5 Measurement of electric fields & all fields above 500kHz
Correct measurement of potential-free electric fields or magnetic fields above
500kHz requires a bit of technical knowledge, as measurement results can
quickly become inaccurate due to objects in immediate proximity, such as walls,
trees, or the operator her-/himself. Consequently, please take care of the follo-
wing:
- You should maximize the distance between your body and the measurement
instrument.
Consequently, you should measure by using a non-conduc
tive, wooden tripod or similar,
and increase the distance between
your body and the device to about 1-2m. Also, please note that these fields
quickly diminish in proximity to the floor. Thusly, most measurements
of electric fields are carried out at a height of about 1-3m above the floor.
Should you wish to measure with the instrument in your hand anyway, you
should only measure with your arm extended. Also, only handle the device
by its tail end, as the sensors are located close to the front of the case.
However, please note that the measured values will be 3 to 4 times too
8.0 Correct measurement
Firmware V 1.0 / © 2005-2013 by Aaronia AG, D-54597 Euscheid, www.aaronia.com
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