Gigahertz Solutions HF32D Mode D'emploi page 12

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range . The basic rule is: as coarse as necessary, as fine as
possible. In the rare case of power densities beyond the de-
signed range of the analyser ("1" displayed on the left hand side
even in the coarsest range) they can still be measured by inserting
the attenuator DG20, available as an optional accessory, which
makes the instrument less sensitive (by a factor of 100).
Setting Signal Evaluation ("Signal"): The peak HF radiation
value, not the average value, is regarded as the measurement of
critical "biological effects" affecting the organism and to be com-
pared to recommended safety limits.
The average value ("RMS") of pulsed signals is often only a very
small fraction of the peak value. Nontheless it forms the basis of
most of the "official" safety limits regulations. Building biologists
consider this a trivialization.
„Peak hold" (HF38B only) simplifies measurements of the total
exposure by retaining the highest readings for some time (it slowly
drops). Note of caution: Switch on "softly" to avoid switching
peaks, which then will be retained for some time simulating unre-
alistic power densities. If peaks are very short and very high the
holding capacity needs an instant until it is fully charged.
How to execute the measurements
Hold the HF analyzer with a slightly outstretched arm, your hand
at the rear of the instrument.
For a rough first overview it is sufficient to probe for areas of
higher levels of radiation simply by following the audio signals
walking through the rooms of interest, directing the analyser eve-
rywhere and rotating it.
Having identified the area of interest for a closer evaluation,
change the positioning of the instrument in order to analyse the
actual power flux density. This is done
by pointing in all directions including upwards and downwards
in flats to establish the main direction of the incoming radiation,
by rotating the instrument around its longitudinal axis by up to
°
90 to also find the plane of polarisation, and
by shifting the instrument in order to find the point of maximum
exposure and to avoid being trapped by local cancellation ef-
fects.
It is generally accepted to use the highest reading in the room
for comparison with limit or recommended values.
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HF38B – „Range": When switching from 'Coarse' to ‚Medium' for very small
readings, it could happen, that the instrument tolerance of +/- 3 dB full range is
absorbed. In this worst case there may be a factor 4 between the displayed
numbers in ‚Coarse' and ‚Medium'. Example: In 'Medium' you read 150.0
µW/m². If worst comes to worst 'Coarse' might show between 0.6 und 0.03
mW/m² (instead of 0.15 mW/m² which would be the correct value). However,
normally the differences shown will be much smaller. For comparing measure-
ments (e.g. 'before' and 'after') take the same range setting.
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