17
Subject to change without notice
H o r i z o n t a l S y s t e m ( T i m e B a s e )
SCALE
TIME / DIV
X-POSITION
HORIZONTAL
TB/Z
MEM
O
R
Y
MENU
ACQUIRE
RUN
STOP
SET
CLR
37
D
38
37
41
39
42
43
44
40
5 Horizontal System (Time Base)
As well as time base settings, the
horizontal system comprises the
selection of the trigger position, the
zoom functions and the available
modes of signal capture. The knobs
are used for the adjustment of the
time base speed and the trigger po-
sition. The signal capture modes are
selected in the respective menus.
There is a key provided for activating
the zoom function.
Fig. 5.1: Control panel of the
horizontal system
5.1. Capturing modes RUN and STOP
The capturing modes can be selected with the key RUN/STOP.
In RUN mode signals will be continuously captured; depending
on the trigger conditions selected, and displayed, erasing the
previously captured ones. If it is desired to store and further
analyze a signal and to prevent it being overwritten, capture
must be stopped by pushing the RUN/STOP key. While in STOP
mode capture is disabled and the key will light up red.
5.2. Time
base
adjustments
The large knob in the HORIZONTAL section of the control panel
is used for the selection of the time base speed. The time base
speed is displayed in the upper left hand corner above the
graticule. (e.g. „TB:500 ns“) To the right there is the display of
the trigger time position with respect to the normal position.
The normal trigger position is in the center of the graticule
such that 50 % of the signal display is before and 50 % is after
this trigger position. The X POSITION knob allows continuous
adjustment of the X position. The available maximum values
depend on the time base setting. By pushing the key SET/CLR
the value will be reset to its reference position. The arrow keys
37
allow you to change the X position by a fi xed amount of
5 divisions in the respective direction. The key MENU opens
a menu which allows you to set the X position to its minimum
and maximum positions by just a key touch. In addition, there
is a submenu
NUMER.INPUT
which allows entry of an arbitrary
X position.
5.3. Capture
modes
The capture modes are selected by pushing the key ACQUIRE,
this opens a display menu which offers the 5 basic modes of
capture:
– Normal:
In this mode the signals are captured and displayed.
– Roll:
This is a mode especially useful for very slow signals: the
signal „rolls“ slowly untriggered from right to left over the
screen (signals must be slower than 200 kHz).
– Envelope:
In this mode the signal will be displayed as in NORMAL,
but its minimum and maximum excursions will also be
displayed such that, with time, an envelope of the signal
will be displayed.
– Average:
Functions only with repetitive signals. The universal knob in
the CURSOR/MENU section of the front panel is used to set
the number of signal periods for averaging, this is possible
in powers of 2 from 2 to 256. Please note: Averaging reduces
the bandwidth.
– Smoothing:
In this mode continuous averaging is used which allows in-
crease of the vertical resolution at the expense of bandwidth
reduction.
The second menu page is accessed by pushing the soft key
next to the menu „Page 1/2“, here, extended functions are
available:
– RANDOM
SAMPL:
For very fast signals displayed with the fastest sweep speeds
it can be advantageous to switch the instrument to Random
Sampling mode; in this mode very many signal periods are
used to generate a high resolution picture, provided the
signal does not change its shape. This is equivalent to a
sampling rate of approx. 50 GSa/s. The oscilloscope will
not automatically enter this mode, however, it is possible to
select automatic switching to Random sampling
>
20 ns/div..
The mode can be disabled by pushing the soft key.
– PEAK
VALUE:
At very slow sweep speeds fast signal details will not be
visible. By selecting this mode peaks will be detected. This
function can be switched on or off in the menu, it is also
possible to select automatic switching in.
All the preceding functions are normally off. The lowest item in
the soft menu allows you to select the preferred signal capturing
repetition rate, there are 3 options:
– MAX. REP RATE:
In this mode an optimum combination of sampling rate and
memory length used will be selected automatically such that
the signal capturing rate will be maximized.
– MAX. SAMPL. RATE:
In this mode the maximum possible sampling rate will be
used.
– AUTOMATIC:
This mode is the standard mode: the instrument always
selects the optimum combination of capturing and sampling
rates (full memory length used).
5.4. ZOOM
function
The HMO352x oscilloscope features a memory depth of 2 MB
per channel, this allows you to record long complex signals
which can be analyzed in detail with the ZOOM function. Push
the ZOOM key to activate this function. The screen will be par-
titioned into two graticule areas: the top one displays the whole
time base window; the lower one displays the zoomed portion of
it. The zoomed portion will be indicated in the upper display by
two blue cursors. With multi channel displays all channels will
be zoomed by the same factor and on the same portion.
In Fig. 5.2 a signal was recorded for 12 ms, the zoom window
is shown with a time scale of 100 μs/div. The time base speed
display in the left upper corner is shown with a grey background,
the zoom time base display is shown in white. This means that
the large knob in the horizontal menu is now available for chan-
ging the zoom factor. This knob also features a push contact; if
