Gigahertz Solutions HF58B Instruction Manual page 7

Digital High Frequency Analyser HF58B
Note:
To allow for as wide a range of power densi-
ties to be read out without using an external
attenuator, a factor of 100 lies between adja-
cent ranges. That means for example an ac-
tual value of 150 µW/m² will be displayed as
150.0 µW/m² in the range "Medium" and as
0.15 mW/m² in the range "Coarse". Due to
technical reasons the tolerances of the in-
strument are relatively high in this overlap-
ping 1% of the next higher range
Rules of thumb for the interpretation of
the results
Readings in the two adjacent sensitivity
ranges "Medium" and "Coarse" use the
one with the higher value.
Numbers below 0.05 mW/m² shown in the
range "Coarse" are within the range of its
potential zero bias. Use the reading shown in
range "Medium".
4
Power densities of a few hundred µW/m², displayed
as 0.01 up to about 0.30 mW/m² in the setting
"Coarse", are those with the highest measurement
uncertainties as % of the actual values. On the other
hand setting the switch to "Medium" activates an inter-
nal amplifier, which brings with it an additional wavi-
ness of up to +/- 1 dB, depending on the actual fre-
quency analysed. Worst case combined to worst case
could absorb almost +/- 3 dB, the maximum tolerance
of the instrument. For very small readings in "Coarse"
that could result in a factor of 4 difference of the corre-
sponding reading with setting "Medium". Numerical
example: In "Medium" you read 150.0 µW/m². In
"Coarse" you could read up to 0.6 mW/m² or down to
0.03 mW/m² in an extreme case. Normally the differ-
ences shown will be much smaller.
© Gigahertz Solutions GmbH, 90579 Langenzenn, Germany
For comparative measurements (before /
after shielding) use the same range selector
position when possible.
Power densities beyond the designed range
of the instrument (display shows "1" on its
left side with the range set on "Coarse") can
still be measured by inserting the attenuator
DG20_G3, available as an optional acces-
sory. By setting the "Adapter" switch to "At-
4
.
tenuator – 20 dB on your instrument ensures
the correct display of the measurement.
Also available are two HF preamplifiers for
factors 10 (HV10) and 1000 (HV30) as plug-
ins into the antenna input socket
cally the HF58B would have a minimum reso-
lution of 0.0001 µW/m², displayed as 0.01
Nanowatt/m². The actual minimum resolution
depends on the video bandwidth selected.
When the video Bandwidth Switch is set to:
•
•
A list of all ranges, which can be measured
and displayed, is at the end of this brochure.
5
The power level adaptor switch is provided for the
factor HV10 amplifier only, not for the HV1000. The
HV1000, has the decimal point in its correct position.
The numbers are displayed in nanoW/m² instead of
µW/m² which is indicated on the LCD.
5
. Theoreti-
TPmax (Radar) : Approx. 1 nW/m²
TP 30kHz (Standard) : Approx. 0.1
nW/m².
Revision 4.5 (December 2006)
Setting:
Signal Evaluation
Signal Evaluation – Average / Peak
A pulsed signal consists of sections of its
time period with high output and another
sections with zero output. Their maximum
output is the wave peak. The following illus-
tration shows the difference in the evaluation
of a pulsed signal if displayed as an average
value reading or a peak value reading.
HF-energy in µW/qm
peak value: 10
avg. value: 1
e.g. 1 pulse every 10 µS
Note: The peak HF radiation value, not the
average value, is regarded as the measure-
ment of critical "biological effects". The peak
value is displayed in the switch setting:
"Peak". The average value is displayed in the
switch setting: "Average".
An experienced measuring technician will be
able to obtain additional information from the
comparison of average and peak values. Ba-
sic Rule: The more the two measurement
values differ from one another (in 2.4-GHz
cordless phones the ratio can be as high as
1:100.), the higher is the potential of a contri-
bution from e.g. a 2.4-GHz cordless phone or
other pulsed signal source to the total maxi-
mum value.
Still today, some field meters only display
average values. They are of little help when
considering the potential health risks associ-
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