30
Subject to change without notice
The same holds as for envelope: the acquisition may be stopped
by pressing the RUN/STOP pushbutton, STOP will be illumina-
ted. Pressing RUN/STOP again will restart. In order to prevent
an inadvertent entering of this mode the operation of any control
will automatically cause this mode to be reset.
The average mode capture can be stopped by the RUN/STOP
pushbutton
6
which will constantly light. Pressing the RUN/
STOP pushbutton
6
again resets the previous signal display,
starts a new average capture and the pushbutton becomes unlit.
To prevent erroneous signal display, the use of controls that
infl uence the signal display automatically cause a reset and a
new start of the acquisition.
As repetitive acquisitions are needed for calculation of an ave-
rage, single sweep will not be compatible.
8.4 Roll mode capture/display
Roll mode means that the signal(s) will be continuously acquired
without the need for a trigger. Hence all controls, displays and
readouts for the trigger and ZOOM will be disabled. The readout
will show ”rol“.
The result of the last acquisition will be displayed at the right
hand edge of the graticule, all formerly acquired signals will
be shifted one address to the left. The result at the left hand
screen edge will be dropped. There is no waiting for a trigger
and thus the hold off time is minimum. As in any other mode
the signal acquisition may be stopped and restarted any time
with the RUN/STOP pushbutton.
In roll mode the time base available is limited to 50 s/cm to
50 ms/cm. Faster time bases do not make sense as the signal
could not be observed any more. Where the time base was set
outside the limits, it will be automatically changed to the next
value within the limits upon entering this mode.
If a time defl ection coeffi cient between 20 ms/cm and 5 ns/cm
is present and “rol“ mode is chosen, the time base will be set
automatically to 50 ms/cm.
8.5 Peak Detect Auto Off
If (Peak Detect) “Auto“ is present, this way of signal capture
will be automatically switched on if Yt (time base) mode is
present, in combination with time defl ection coeffi cients from
50 s/cm to 500 ns/cm. This capture mode is available if refresh,
roll, envelope, average and single (event) trigger is active. The
readout then displays “PD:...“ in front of the abbreviation for
the signal capture mode.
Without Peak Detect activated, the signal sampling rate is
relatively low at high time defl ection coeffi cients. As a result
there are wide time caps between the samples, and short signal
deviations such as glitches may occur without being sampled.
The maximum gap size is 0.25 s between the samples at a time
base setting of 50 s/cm.
The advantage of Peak Detect is that signals are sampled with
the highest possible sampling rate to reduce the gap size, so that
even signals with a pulse width of
>
10 ns can be recorded. This
increases the number of signal data that must be evaluated so
that only those samples are displayed with the highest deviation.
Without glitches the deviation is caused by noise.
8.6 Random Auto Off
Provided single sweep was not selected, Random Sampling will
be automatically selected beginning at a certain sweep speed.
The time base setting will be indicated in the readout, e.g.
”RS: 20 GSa“ (= Random sampling with 20 GSa/s effective
sampling rate), the real time, time base speed will be 5 ns/cm.
Without Random Sampling ”RS“ Real Time Sampling will be used
with a maximum sampling rate of 2 GSa/s (one channel only) or
1 GSa/s (two channel mode).
Random Sampling requires repetitive signals, each signal peri-
od will contribute one sample. At an effective sampling rate of
20 GSa/s the time difference from sample to sample along the
signal period will be 0.05 ns. However, note that with random
sampling the samples are not taken in sequence along the signal
period but randomly with respect to the trigger point. Random
Sampling allows it to generate the 200 points per cm in X direction
at the fastest time base of 2 ns/cm.
Remark:
2 ns/cm is also available in other modes. In Real Time Sampling
mode and 2 GSa/s on one channel each 0.5 ns a sample is taken,
hence at 2 ns/cm there are 4 points per cm. The ”missing“ 196
points are generated by interpolation using sin x/x.
STOP
Remark:
2 ns/cm is also available in other modes. In Real
Time Sampling mode and 2 GSa/s on one channel
each 0.5 ns a sample is taken, hence at 4 ns/cm the-
re are 4 points per cm. The ”missing“ 196 points are
generated by interpolation using sin x/x if “Vectors”
or “Optimal” is chosen in the menu Settings Display.
9
SAVE
/
RECALL
(pushbutton)
This pushbutton will open up a menu. The number of choices in this
menu is dependent upon analog or digital mode being selected.
9.1 Analog and digital mode
Under ”Save/Recall“ the current instrument settings may be
saved, or settings saved earlier recalled. There are 9 non volatile
memories available.
9.1.1
Saving the actual settings
The function key “Save” opens the submenu “Front Panel Save”.
The function key “Page 1 2” is for page selection; the page
chosen is indicated by intensifi ed brightness. Page 1 offers the
memories 1 to 5 and page 2 the memories 6 to 9. The instrument
C o n t r o l s a n d R e a d o u t
INTENS
!
HM2008
2 GSa
·
2 MB
200 MHz
DIGITAL
ANALOG
FOCUS
TRACE
MENU
CURSOR
MEASURE
MATH
SAVE/
RECALL
AUTOSET
RUN / STOP
ACQUIRE
SETTINGS
HELP
ANALOG
DIGITAL
MIXED SIGNAL
OSCILLOSCOPE
POWER
POWER
MENU
OFF
1
11
2
3
4
5
6
7
8
9
10
12
