Save/Recall; Autoset; Position; Auto/Norm -Led Button - Hameg HM400 Handbuch

F u n c t i o n o f t h e c o n t r o l s
8
control is disabled; the X position is always controlled by the knob
HORIZONTAL position 17 .
Measurement of DC voltages
If there are no voltages present at the Y amplifi er inputs
was selected, the trace positions correspond to zero volts, however, they
are also infl uenced by the position controls! (The trace will be visible
only if automatic triggering AUTO
In order to measure a DC voltage, fi rst the input must be disconnected
or switched to GND. Then it is up to the user to choose a reference
trace position with the respective position control, i.e.
1. Then the dc voltage can be connected resp. the input switched from
GND to DC; the trace will move by an amount depending on the polarity
and value of the dc voltage and the sensitivity (and probe) selected. The
same is true for measuring the dc content of any signal.
In regular operation, the position controls will mostly be set to the
screen center representing zero. It should be kept in mind, that it can not
be just assumed that a trace position at the screen center corresponds
to zero volts, this has to be checked by switching to GND.
9

SAVE/RECALL

This button allows access to the settings memories in conjunction with
the mode buttons 41 to 46 . 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 41 to 46 will light up. By pressing the desired mode button, the
settings stored in that memory will be taken over by the oscilloscope.
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.
10

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).
11

POSITION 2

This is the position control knob for channel 2 (CH 2). In the ADD mode
8
both position controls , 11 are effective. In XY mode this knob will
control the Y position; the X position is always controlled by the X po-
sition control 17 .
Measurement of dc voltages.
See the paragraph under POSITION 1
12 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.
40 Subject to change without notice
38 , 39 or if GND
12 was selected.)
8
for channel
41 to 46 start blinking. By pressing
8
.
1 2 3 4 5 6 7
ADJUST SELECT
POWER POWER
!
INTENS
+ +
FOCUS
TRACE
SAVE push long
RECALL
POSITION 1 POSITION 2
1 1–6
CH1 CH1
AUTOSET
2
CH2 CH2
8 9
10 11
AUTO
Automatic triggering is available with or without peak-to-peak measure-
ment. The TRIGGER LEVEL 14 knob is active in both cases. The auto-
matic 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
14
TRIGGER LEVEL control is set inappropriately for the signal applied.
The best procedure is to use auto peak-to-peak triggering as the stan-
dard and use NORM only if necessary.
13
SLOPE – LED button
This button selects either the plus or the minus slope of the triggering
signal. The LED will light up if the negative slope is selected.
14
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 10 will restore a triggered display in most cases.
15 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.
16 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 17 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.
12 15
HM400
40 MHz ANALOG OSCILLOSCOPE
AUTO TRIGGER TRIG'd
X-POSITION
LEVEL
NORM
SLOPE
X-MAG
x10
13 14 16 17
14 con-