Normal Operating Mode And Zero Span Mode; Controls And Readout - Hameg Instruments HM5530 Manual Del Usuario

F u n c t i o n a l p r i n c i p l e o f t h e H M 5 5 3 0
fi lter, VBW). It is then a/d converted, so the following signal processing
is digital. The signal data are stored in a RAM, the lowest frequency at
the lowest address, the highest at the highest address.
The data in this memory (A) are continuously updated i.e. overwritten by
new data, while they are being read out and reconverted to an analog
signal by a d/a converter. This analog signal is amplifi ed and applied
to the Y defl ection plates of the CRT. With increasing signal amplitude
the trace will be logarithmically defl ected in positive direction. The full
screen dynamic range is 80 dB (10 dB/div.) or 40 dB (5 dB/div.). This
dynamic range can be shifted through the whole dynamic range of the
instrument by setting the reference level between –110 and +20 dBm.
This is analogous to the difference amplifi er with offset of a scope.
The RAM addresses are d/a converted into a staircase voltage which
is amplifi ed and applied to the X defl ection plates of the crt. The si-
gnal with the lowest frequency is displayed at the left of the graticule
(START), the signal with the highest frequency at its right (STOP). The
same signal tunes the 1st local oscillator through the range (CENTER
frequency ± ½ SPAN) selected, the time for one sweep is indicated in
the readout (SW ... ).
The frequency range swept as determined by the SPAN setting and the
resolution bandwidth (RBW) are related by physical laws, if these are
violated, the amplitudes displayed will be too low. Such errors will accrue
if the sweep speed is too high compared to the narrowest bandwidth of
the combined fi lters including the video fi lter: The narrower the fi lter
bandwidth, the slower the sweep speed, otherwise the fi lters are not
allowed suffi cient response time to reach full amplitude. The instrument
will indicate illegal combinations of bandwidth and sweep speed by
UNCAL in place of the sweep speed readout (SW ... ).

Normal operating mode and ZERO SPAN mode.

Basically, there are two operating modes: swept (SPAN unequal to 0, i.e.
1 to 3000 MHz with the HM 5530) and sweep off or ZERO SPAN.
st
In ZERO SPAN mode, the 1 LO is not swept, but generates a fi xed fre-
quency, set by the CENTER adjustment, which is 3537.3 MHz above the
input (CENTER) frequency. The analyzer will then only display the level
of that one frequency by a logarithmic shift of the baseline in vertical
direction. This is similar to a scope which displays (linearly) a pure dc
level. The analyzer thus becomes a frequency selective voltmeter.
In normal mode (SPAN 1 to 3000 MHz) a frequency range equal to the
SPAN setting will be displayed. If the center frequency is e.g. 500 MHz
and the span 1000 MHz, the measurement will start at the left of the
graticule at 0 kHz and stop at its right at 1000 MHz; the frequency of
st
the 1 LO will be swept by the staircase voltage from 3537.3 to 4537.3
MHz. The HM5530 also provides for the direct setting/readout of START
and STOP frequencies.
The stored data may be further processed or transmitted to a pc via the
serial interface. The instrument can also be remotely controlled that
way. Available functions are: Average, Max. Hold, Min Hold, Copying of
a spectrum from memory A to memory B, display of the contents of
memories A or B, display of the difference of memories A – B. All these
operations are performed digitally.
The manually or automatically selectable reference level (REF.LEVEL)
which can be varied from –110 dBm to +20 dBm as well as the two
markers allow the easy acquisition of numerical measurement results.
Both markers can also be automatically positioned on the peak of the
spectrum displayed, the deltamarker indicates the difference frequency
and the difference amplitude between markers.
The instrument further features a test signal output (reference spec-
trum) which may be used for instrument self tests by connecting it
to the input. There is also an input for an external trigger which can
trigger a sweep.
30
Subject to change without notice

Controls and readout

Functions designated with an asteric * are called by a long depression
of the pushbutton.
With the exception of DISPLAY MODE, dB/dic., 2 x ATT, COPY A to B,
keyboard all pushbuttons light up when depressed and remain lit as long
as the function is active. A function is disabled by calling another one.
Prior to entering a number via the keyboard, the respective function key
must be lit, else it has to be fi rst depressed. The entry will appear at
the bottom of the left readout fi eld, the function selected is shown. The
entry will be accepted after depressing the lighted function pushbutton
(again); the entry display will disappear. Entries which would exceed a
specifi ed maximum or minimum will not be accepted; the instrument
will set the respective maximum or minimum value allowed, there is
no acoustical warning.
The tuning knob (rotary encoder) is always active if any of the function
pushbuttons listed under is lit. Entries which would exceed a maxi-
mum or minimum specifi ed will not be accepted; the instrument will
set the respective maximum or minimum value allowed, an acoustical
warning is sounded.
POWER
Power (mains) switch with the symbols I for ON and
The switch will latch in the ON position; after the time required by the
crt for heating has elapsed, the HAMEG logo will be displayed, then the
fi rmware version; the intensity is fi xed in order to ensure a readable
display irrespective of the setting of the intensity control and to forecome
the impression the instrument might be defective.
After the fi rmware display, the instrument will enter its operational
mode: the two readout fi elds will appear at the top left and right of the
screen, and the pushbuttons CENTER and WRITE A will light up. At the
bottom of the screen the more or less wide noise band will show up,
even if there is no input signal.
Note:
Upon turn-off, all memory contents are lost with the exception of the
memories which store the functions and numbers displayed in the 8
readout fi elds. The functions and numbers shown last at the time of
turn-off will be reinserted in the 8 readout fi elds. Irrespective of the
function pushbuttons which were active at the time of turn-off, only
CENTER and WRITE A will light up after turn-on.
Keyboard
10 numerical keys plus a decimal point key are provided for number
entry of the following parameters: Center frequency CENTER
, START frequency , STOP frequency
, REF.LEVEL , TEST signal level
The key C/ESC* has a triple function: minus sign, short depression:
erase of one digit of the entry, long depression: erase of the whole entry
in the readout entry display fi eld.
Prior to any number entry, the respective function pushbutton, e.g.
CENTER , must be lit already, else it must be depressed fi rst. The
entry is shown in the bottom line of the left readout fi eld, together
with an indication of the function selected. The entry is accepted after
depressing the function pushbutton (again); the entry display will dis-
appear. If an entry is made and then a pushbutton depressed which
was not lit, the entry will be ignored and erased. Entries which would
exceed a specifi ed maximum or minimum will not be accepted, the
instrument will set the maximum or minimum allowable values. No
acoustical warning is given.
for OFF.
, SPAN
, MARKER / Δ -MARKER
.