Save/Recall; Autoset; Auto/Norm -Led Button; Slope - Led Button - Rohde & Schwarz Hameg HM400 Manuel

6
SAVE / RECALL
This button allows access to the settings memories in conjunction
with the MODE buttons 32 . The oscilloscope has 6 settings memories,
settings can be stored or recalled.
SAVE: In order to store a setting, fi rst press the SAVE/RECALL button
for some time, until the MODE buttons
the respective mode button, the associated memory will be called and
the present setting will be stored, the mode button LEDs will then
extinguish. If the SAVE/RECALL button was pressed inadvertently,
this can be repaired by pressing it again or any other button except
the mode buttons.
RECAL: For recalling press the SAVE/RECALL button just shortly, the
mode buttons 32 will light up. By pressing the desired mode button,
the settings stored in that memory will be taken over by the oscil-
loscope. The mode buttons will then extinguish. If the SAVE/RECALL
button was pressed inadvertently, this can be repaired by pressing it
again or any other button except the mode buttons.
Please note that the signal presently displayed should be
similar to that which was present at the time the setting
was stored! If any other signal (frequency, amplitude)
is being displayed when recalling, seemingly „false"
STOP displays may result as the recalled settings may not be
appropriate for the other signal.
7

AUTOSET

See also the chapter AUTOSET. Pressing this button will cause the
instrument to automatically choose a setting which generates a
meaningful display. If the modes XY or Component Tester were active
before pressing this button, AUTOSET will switch to the Yt mode last
used (CH 1, CH 2, DUAL).
8 AUTO / NORM –LED button
By pressing this button shortly the trigger mode will be alternated
between AUTO and NORMAL triggering. The LED will light up when
NORMAL triggering is selected.
AUTO: Automatic triggering is available with or without peak-to-peak
measurement. The TRIGGER LEVEL
automatic triggering circuit will also provide a bright baseline if there
is no signal or an insuffi cient one for triggering. See the specifi cations
for the lower frequency limit below which automatic triggering does
not function, i.e. the display will not be triggered.
With peak-to-peak triggering the range of the TRIGGER LEVEL
trol will be automatically adjusted to the present peak-to-peak signal
level. Without this function there is no relationship between the signal
amplitude and the range of the trigger level control, hence the trigger
level may then be set too high or too low. The automatic triggering circuit
will display the signal, but it will not be triggered.
Whether peak-to-peak triggering is active or not depends on the ope-
rating mode and the trigger coupling selected. By turning the TRIGGER
LEVEL knob and looking for the start of the display, it will be obvious
whether it is active or not.
NORM: This is called the normal mode because it is the only one which
allows triggering of complex waveforms and of very low frequency
signals; in this mode the automatic and the peak-to-peak functions are
disabled. A disadvantage of this mode is the fact that there will no trace
visible if there is no signal, if the signal is insuffi cient for triggering or
if the TRIGGER LEVEL 10 control is set inappropriately for the signal
applied. The best procedure is to use auto peak-to-peak triggering as
the standard and use NORM only if necessary.
9 SLOPE – LED button
This button selects either the plus ( ) or the minus ( ) slope of the trig-
gering signal. The LED will light up if the negative slope is selected.
32 start blinking. By pressing
10 knob is active in both cases. The
10 con-
F u n c t i o n o f t h e c o n t r o l s
10 TRIGGER LEVEL – Knob
With this control the level of the triggering signal is determined at which
the trigger comparator will respond and generate a signal to start the
time base. The slope is selected with the above slope button. The trig-
ger point is the point on the signal at which the display starts, it can be
moved along the signal with the TRIGGER LEVEL control. See also the
explanations in the foregoing paragraphs about automatic, peak-to-
peak and normal triggering. In some combinations it is possible to loose
triggering if the trigger level control is not set appropriately. Pressing
AUTOSET 7 will restore a triggered display in most cases.
11 TRIG'd – LED
This LED will light if up the time base receives start pulses from the
trigger comparator. Depending on the frequency of the pulses the LED
will blink or appear to light steadily.
12 X-MAG/ x10 – Button with „x 10" LED
This button switches the X magnifi er on/off, the LED wil indicate if
the magnifi er is on. The magnifi ed portion of the display can be shif-
ted with the X-POSITION 13 control. The magnifi cation expands the
display around the screen center, hence the normal procedure is to
move the portion to be magnifi ed to the center with the X-POSITION
control and then to activate the magnifi er. In XY mode the magnifi er
is disabled.
13 X-POSITION
With this knob the display can be moved in X direction (horizontally). See
the paragraph above for its use together with the magnifi er.
14 VOLTS/DIV, CH1 + CH2 – knobs
These are dual function knobs: it is used to select the appropriate
sensitiviy for the signal of each channel's input, by pressing it shortly
it will assume the „Variable" (VAR) function (see below), while this is
active, the sensitivity indicators (ring of LEDs around the knob) will blink
as a warning that the sensitivity is now uncalibrated. The knob is only
enabled if CH1 or CH2 was activated or selected as the trigger source
(CH1 or CH2 only, dual trace, ADD, XY).
Sensitivity selection (Input attenuator)
If the sensitivity indicator LED does not blink, the sensitivity selected
will be calibrated. The sensitivity can be decreased CCW to 20 V/DV and
increased CW to 1 mV/DIV in 1 – 2 – 5 steps.
VAR (CH1 + CH2)
By pressing the VOLTS/DIV 14 knobs shortly, its function will be changed
to „Variable" which will be indicated by blinking of the sensitivity indicator
LEDs around the knob. Pressing it again will restore the calibrated
sensitivity, the blinking will stop. As long as the variable function is
enabled, the display will be uncalibrated! CCW rotation will decrease
the sensitivity, CW rotation will increase it. The variable allows hence
to bridge the 1 – 2 – 5 steps of the sensitivity switch. If any of the two
limits of the variable range is reached, an acoustic signal will indicate
this. This function is frequently used e.g. for measuring rise times: be-
cause the rise time is defi ned from 10 to 90 % of the full amplitude, the
variable comes in handy to set the (uncalibrated) signal amplitude e.g.
precisely to 6 divisions peak-to-peak; by shifting the display horizontally
with the X position control, the rise time can be read from 6 mm from
the bottom to 6 mm below the top of the waveform.
15 TIME/DIV – knob
This knob has a triple function:
1. It selects the time base speed.
2. By pressing it shortly, it will assume the „Variable" VAR function,
this will be indicated by blinking of the LEDs around the knob.
3. After pressing the HOLD-OFF/ON
function of hold-off time adjustment, this will be indicated by the
button 27 lighting up, refer to
The time base speed is selectable in 1 – 2 – 5 steps, turning the knob
CCW, it can be decreased to 0.2 s/DIV, turning it CW, it can be increased
to 100 ns/DIV, the speed will be indicated by the LEDs around the knob,
27 button, it will assume the
27 .
Subject to change without notice
37