Hameg Instruments HZ530 Manual Del Usuario página 46

Will a screened room overcome the problem of ambient signals?
Can I make meaningful radiated emissions measurements
with a near field probe instead of an antenna?
Do spectrum analyzers have any advantages over receivers?
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radiated emissions measurements. In some industrial environments,
the existing ambient may make obtaining radiated emissions measu-
rements very difficult. There is no advantage in using compliance
instruments in such locations.
Any Faraday cage structure provides screening from externally ge-
nerated ambient signals. However, in an unlined screened room, any
electromagnetic energy inside from the unit under test, for instance
- reflects from all the metallic surfaces of the room. The result is
a very uneven and position sensitive field, and you will measure
different levels depending on the positions of both the unit and the
antenna. You may encounter errors up to ±40dB irrespective of
the instruments you use.
The two types of measurements are different. In fact, they are
complementary and not alternatives. A near field probe only ope-
rates in the "near field", whereas an antenna operates in the "far
field". In the near field you cannot easily quantify the impedance of
the source, whereas in the far field the impedance of free space
is a constant 377 Ω.
For example, a near field probe allows you to detect RF currents
on printed circuit boards, and consequently enables you to pin-
point problem signals that you first observed using an antenna on
an open area test site. If you are going down to detect the source
of the radiation (e.g. a transistor, IC, or any other component) on
the contact-level, the high-impedance probe of the HZ530 probe
set is indispensable for measurements due to its ultra-low input
capacitance of 2pF only.
Yes. Spectrum analyzers are generally more flexible, particularly for
design and diagnostic testing. The main advantage is that you can
observe large frequency spans, whereas a receiver only displays
one amplitude and one frequency at a time. An additional advan-
Änderungen vorbehalten / Subject to change without notice