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3.4.3.3. AUTO triggering and HOLD OFF
In the AUTO PP mode, the MTB starts automatically
rated
in the AUTO
Even with no signal applied to the input of the oscilloscope, a trace will be visible on the screen in the AUTO PP
mode. As soon as trigger pulses are available, the free-running state of the MTB is terminated and it is triggered
within the AUTO peak-peak level.
This peak-peak level is determined by the amplitude of the input signal, asdescribed in Section 3.4.3.2.
When the AUTO PPand TRIG pushbuttons are depressedtogether, the time-base is triggered as in the AUTO PP
mode, but without AUTO peak-peak level, as previously stated. In this mode, the trigger signal coupling is
determined by the MTB trigger coupling switches.
The oscilloscope also features a variabte HOLD OFF control. This performs a useful function
computer applications, where complex pulse patterns need to be measured.
When a complex pulse pattern is displayed (see Fig. 3.4.) and this pattern is also used for triggering, a double
or even a multiple-picture display may occur. The more complex the pattern, the greater the possibility of
multipie
displays.
These effects can be corrected by adjusting the HOLD OFF control to increase the hold-off time (see Fig. 3.4.)
Normally, the HOLD OFF control should be fully clockwise to maintain trace brightness at the faster sweep
rates.
2
Fig. 3.4. Trigger pulse suppression with the variable HOLD OFF control
3.4.3.4. SINGLE shot triggering
When events that occur only once need to be observed, it is often desirable to ensure that only one sawtooth
is generated, even though further trigger pulses occur after the phenomena of interest. To this end, the
SINGLE pushbutton
The first trigger pulse to occur, after the SINGLE pushbutton
the MTB does not respond to trigger pulses until the SINGLE
Adjust the LEVEL control so that the NOT TRIG'D
The NOT TRIG'D
of the MTB sweep; i.e. after triggering.
So the "NOT TRIG'D"
from screen. This detection goes up to one nanosec pulses (Glitch catching!).
X Magnifier
When the push-pull switch X MAGNI combined with the X POS control, is pulled, the sweep speed on the
screen increases to ten times the TIME/DIV
In this position, the portion of the signal, displayed ever a width of one division in the centre of the screen in
the xl position (X MAGN depressed), will occupy the full width of the screen.
Using the X POS control, any portion of the trace can be brought on to the screen for inspection.
In the x 10 position, the time coefficient
The X MAGN is also operative in all the X DEFL modes.
circuit.
2
2
3
(VARIABLE
HOED
FIXED
HOLD
OFF
of the MTB trigger mode selector must be selected.
indicator lights up when the SINGLE pushbutton
LED may be used to detect short, non recurrent, spikes which are too fast to observe
setting of the time-base.
is determined by dividing the TIME/DIV
when no trigger pulses are available, by trigger pulses gene-
3
SIGNAL
TO BE DISPLAYED
MTB
SWEEP
HOLD
OFF SIGNAL
OFF
MAT
942
has been depressed, starts the MT B. After this,
pushbutton
is again depressed.
indicator extinguishes.
is depressed and extinguishes at the end
37
in digital and
setting by a factor of 10.
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