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11
If switch "DEL'D TRIGG." is in position "STARTS
A" (this means that time-base A is triggered by the
delay pulse), the delay time will be equal to the
product of the values indicated by knobs "DELAY
TIME" and "DELAY TIME MULTIPLIER". In
Fig. 5 the delay time amounts to: 3.86 X 50 µsec.
= 193 µsec.
The magnitude of the intensified part of the trace
depends on the time co-efficient of time-base A and
should consequently be adjusted by means of knob
"TIME/cm" on the basic oscilloscope.
If switch "DEL'D TRIGG." is in position "SETS
A READY", time-base A is released by the delayed
trigger pulse. Time base A will be triggered by the
next pulse, generated at the trigger unit of the basic
oscilloscope.
The adjustment of time-base "A" then is effected in
the same way as with normal use of this time-base
(refer to manual PM 3330) with the restriction that
position "AUT." of the "TRIGGER-MODE" switch
may not be used.
A~~lications
The PM 3347 is particularly used when details of a
complicated, periodical signal are to be measured.
Assume that the display (Fig. 6) is obtained in posi-
tion "TIME-BASE B" of the deflection switch on the
PM 3347.
Time-base B is then triggered by the clock-pulse, by
which the pattern is always started.
In this example the clock-pulse has a higher amplitude
than the other pulses. Consequently, the time-base
may be internally triggered. I f all pulses have the same
amplitude, no stable display is obtained with internal
triggering. In that case the time-base should be trig-
gered by an external voltage.
When pulse P is to be accurately measured, the
deflection switch should be set to position "B IN-
TENSIFIED BY A" and switch "DEL'D TRIGG."
should be set to position "STARTS A".
With aid of control "DELAY-TIME MULTIPLIER"
and switch "TIME/cm" of the basic oscilloscope,
part P of the display is intensified.
When the deflection switch is then set to position "A
DEL'D BY B", the intensified part (magnified across
the entire screen) is reproduced.
In this position, pulse-width, rise-time etc. can be
accurately measured by means of the calibrated time
coefficients of time-base A.
The time T (delay time of pulse P with respect to
the clock-pulse) can be measured by adjusting knob
The adjusted value of the delay time is then increased
by an additional time, which depends on the trigger
signal of the basic oscilloscope. Consequently, the
adjusted value of the knobs on the PM 3347 no
longer applies.
LENGTH
If long delay times are used (time-coefficient of
time-base A much smaller than the time coefficient
of time-base B), time-base A will have a very short
duty cycle. This means that the brightness of the
trace in position "A DEL'D BY B" is very low with
respect to the other positions.
By adjusting the length of the time-base in the posi-
tion "B INTENSIFIED BY A", so that the intensified
part of the trace just remains present, the repetition
frequency of time-base B can be increased in many
cases.
Consequently, the repetition frequency of time-base
A is increased and the luminosity increases also.
"DELAY-TIME MULTIPLIER" so, that the lead-
ing edge of pulse P just coincides with the beginning
of the time-base.
T is equal to the product of the values indicated by
knobs "DELAY TIME MULTIPLIER" and "DE-
LAY-TIME".
f l
Fig. 6. Example of a display
K
T
P
--•, ~.-
P
1
Fig. 7. Measuring time "T"
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