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If the QG 502 is driving
the 1 Ma capacitively-shunted
vertical
input
of a" oscilloscope,
connect
a 50 a termina-
tion
to the oscilloscope
input.
Connect
the coaxial
cable
from
the PG 502 to a 50 a 10X attenuator,
and connect
the attenuator
to the termination.
The attenuator
isolates
the input
capacity,
providing
a" improved
termination
for
the cable. Another
method
is to back terminate
the PG 502
by pulling
The BACK
TERM
(PULL)
pushbutton
on the
front
panel,
and
connecting
the
coaxial
cable
to the
oscilloscope
input through
a 50 fi termination.
Risatima
Measurements
in Linear Systems
Consider
the rise and fallfime
of associated
equipment
when measuring
the rise or falltime
of a linear device. If the
risetime
of the device tinder tesl is at least ten times slower
than the combined
risetimes of the QG 502. the monitoring
oscilloscope,
and acsociated
cables, the error
introduced
will not exceed I%, and usually
may be ignored.
If the rise
or falltime
of the test device is less than ten times slower
than the combined
risetimes
of the testing
sysw",
deter"
mine the actual
risetime
of the device under test by using
the following
formula:
R,
equals
the
overall
rise
or
falltime
of the
entire
measurement
system and R,, R,. R,, etc. are the risetimes
or falltimes
of the individual
componentc
comprising
the
system.
-
rrl
I
I
Variable
Pulse Delay
Variable
pulse delays
may be obtained
using another
PG 502,
or other
suitable
pulse generator.
For example,
using two PG 502s. push the COMPLEMENT
button
and,
using
a" oscilloscope,
set the OUTPUT
(VOLTS)
LOW
LEVEL
control
on rhe delay
generator
for 0 V. Set the
HIGH
LEVEL
control
for +I V. Some fine luning
of the
output
levels of this generator
may be necessary to achieve
250 MHz operation.
Connect
the OUTPUT
from the delay
generator
to the +TRIE/DURATION
INPUT connector
on
the output.
generator.
Take
the pulse
output
from
the
I
OUTPUT
connection
on the
output
generator,
and the
trigger
from
the + TRIG
OUT
connector
on the delay
generator.
The PERIOD
controls
on the delay
generator
now set
the period
of the output
waveform,
and the DURATION
controls
set the delay.
The
output
pulse
duration
and
voltage
levels are set by the appropriate
controls
on the
I
R, = YH , + H 2 + R 3
output
generator.
See Fig. I-3
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