Hameg Instruments HM5530 Manual Del Usuario página 32

C o n t r o l s a n d r e a d o u t
Tuning knob (rotary encoder)
Rotary encoder for the parameter entry or change of:
Center frequency CENTER , SPAN
, MARKER / Δ -MARKER
frequency
level , Intensity INTENS , FOCUS
PHONE .
Any entry which would exceed a specifi ed maximum or minimum value
will not be accepted, the instrument will set the maximum or minimum
allowable value, a warning will be sounded.
DISPLAY MODE
Depressing this pushbutton once will dim the character readout
intensity. The switching sequence is 100%, 50%, 0% and then again
100. A second depression turns the character readout off. A third one
will restore the initial setting. The activated interface (RS-232 or USB)
can be indicated by long pressing (only in connection with the option
HO720). The interface (RS-232 or USB) can be selected by repeated
short pressing.
INTENS
The intensity can be varied with the tuning knob
increase, CCW rotation will decrease the intensity. It is recommended
to increase the intensity only so much as is needed for a well visible
display, any higher setting will not reveal any more details but defocus
the trace, also the life of the phosphor in the area of the noise baseline
will be impaired.
FOCUS
The focus can be adjusted with the tuning knob
re is to fi rst set the intensity and then to adjust the focus for uniformity
over the whole screen.
TRACE
The trace rotation can be adjusted with the tuning knob
pressing this pushbutton a rectangle with a horizontal center line will be
displayed; this line can be rotated with the tuning knob until it is parallel
to the graticule center line. In spite of the crt shield provided residual
infl uences of the earth's magnetic fi eld may require a readjustment
when the instrument was moved. A slight barrel or pincushion distortion
can not be corrected and has no infl uence on the measurements.
dB/div. - dB unit (push long)
Short depression: alternation of scaling between 10 and 5 dB/div.
Display in the righthand readout to the right of the attenuator value
(AT...dB ... dB/).
Long depression: cyclic change of the unit from dBm to dBmV to dBμV.
The unit selected will be shown in all applicable readout fi elds: (RL ...
dBm), (ML ... dBm), (TL ... dBm). This pushbutton does not light up.
ATTENUATION L M (0 dB)
These two pushbuttons (which do not light up) switch the input atte-
nuator from (0) 10 to 50 dB in 10 dB steps. Display in the right readout
fi eld (AT ... dB).
„0 dB *" means that this position of the attenuator (no
attenuation) can only be switched in by an intentional long
depression of the upper pushbutton. This is provided for
safety reasons in order to minimize the danger of destruc-
tion of the input stage.
STOP
Please note carefully that the maximum specifi ed values for the input
signal level and a dc content must not be exceeded! This is especially
important because a spectrum analyzer will not show signals outside its
specifi ed range (0.1 to 3000 MHz) and also, depending on the settings,
may display only a portion of the spectrum within its range; excessive
levels outside the displayed spectrum may cause destruction of the
input stage.
32
Subject to change without notice
, START frequency , STOP
, REF.LEVEL , TEST signal
, TRACE rotation , volume
, CW rotation will
. The correct procedu-
. After de-
REF.LEVEL / AUTO (push long)
Short depression: adjustment of the reference level either by keyboard
entry or with the tuning knob
button must be lit, else it must be depressed fi rst. The tuning knob will
be active immediately; a keyboard entry will be displayed in the last line
of the left readout fi eld, it will be accepted after a (second) depression
and displayed in the reference level readout (RL ... dBm), the entry
display will disappear. Legal values are –110 to +20 dBm.
AUTO means that the analyzer can be switched to automatic reference
level selection by a long depression; this will be indicated in the readout
by (RL * ... dBm). Please note that the 0 dB attenuator position will not
be used in automatic mode. The AUTO mode is left by another long
depression.
Should the noise band already reside at the graticule bottom, the refe-
rence level can not be increased any further, i.e. the noise band can not
be positioned farther down, a warning will be sounded. The reference
level can then only be decreased, i.e. the noise band shifted upward;
this will, however, also decrease the available dynamic range.
The noise band will disappear altogether, if it was already positioned at
the graticule bottom, if the scaling
will become visible again by decreasing the reference level.
Interpretation of measurement results
The measurement results shown in the readout fi elds take all settings
into account automatically, also the input attenuation; hence all num-
bers displayed represent the true values at the measurement points
selected in dBm, dBmV, or dBμV, as selected.
The reference level refers to the top graticule line, from
which all measurements are to be derived downward!
This is exactly the opposite of the procedure with oscillos-
copes. If the reference level is, e.g. RL = 0 dBm, the bot-
tom graticule line corresponds to –80 dBm at 10 dB/div. or
STOP
–40 dBm at 5 dB/div.
The reference level is equivalent to an offset voltage with scopes, it
can be selected within the permissible range of –110 to +20 dBm in
order to facilitate readings; it has no infl uence on the sensitivity or the
calibration. Quite comparable to a difference amplifi er with offset, the
dynamic range window of 80 or 40 dB can be shifted within the reference
level range.
There are two options for obtaining numerical results: directly from the
screen or by use of the markers.
When reading from the screen display, one counts the divisions (cm)
from the reference level at the top graticule line downward to the point
of interest and multiplies the divisions with the scaling factor, e.g. 10
dB/div. If the reference level is, e.g. , RL = 0 dBm, and if the point to be
measured 1 div (cm) below, its true level will be –10 dBm.
Much easier is the method of calling the fi rst marker by a short de-
pression of MARKER and of positioning it with the tuning knob to
the point of interest: the level and the frequency can be read directly
from the readout (ML ... dBm), (MF ... MHz). In practice, mostly the
levels of spectral peaks are of interest. By a second short depression
of the MARKER pushbutton the marker will be positioned automatically
on the highest peak of the spectrum displayed.
See MARKER for a description of the marker functions.
VBW (Video bandwidth)
This pushbutton switches a video fi lter in which reduces the video band-
width from 50 to 4 kHz, indicated in the left readout fi eld (VB 4 kHz). The
use of this low pass attenuates the noise and increases the visibilty of
weak signals. This fi lter should not be used with pulsed signals.
. Prior to any adjustment, the push-
is switched from 10 to 5 dB/div. It