Tektronix TYPE CA Instruction Manual page 10

CHOPPED
When it is necessary to observe a single
transient at two parts
procedure must be followed. In the foregoing
case, one of the signals triggers the sweep
and that amplifier remains conducting for the
sweep duration. At the end of the sweep the
amplifiers are switched and the other signal
then triggers the sweep and that amplifier
remains conducting for the sweep duration.
Each of the signals is being displayed every
other sweep cycle. If you attempted to observe
a single transient in this manner the transient
will pass through whichever amplifier happens
to be conducting
This will display the transient as seen by
whichever amplifier is conducting but when
the amplifiers are switched at the end of that
sweep there will be no further signal to trigger
another sweep until the next transient occurs.
The problem here is to be able to observe
the transient using both amplifiers during a
single sweep cycle.
Turn the MODE switch to CHOPPED. Now
the two amplifiers are being switched on and
off independently of any signal. The switching
rate is approximately 100 kc so each amp ­
lifier is conducting for about
is cut off while the other amplifier conducts
for an equal length of time.
It will usually be very difficult if
impossible to trigger the sweep internally from
the signal so the triggering controls should
be set for external triggering. The external
triggering signal should bear a definite time
relationship to the displayed signals.
2-4
http://manoman.sqhill.com
of a circuit another
and will trigger the sweep.
5 μ sec and then
Operating Instructions - Type CA
It is possible that the
waveform could end
100 kc switching waveform.
is possible particularly if the
traces are positioned very far
The two signals to be observed
nected to the two inputs and both
will be displayed during one sweep
sients as short as
well delineated, with
each trace. As before, the independent
of each amplifier will allow you
attenuate, or invert the
can be easily compared.
ADDED ALGEBRAICALLY
In many applications, the desired signal
superimposed on an undesired signal such as
line frequency hum, etc. The Algebraic Output
of the Type CA unit (with the MODE switch
in the ADDED
makes it possible in many cases to improve the
ratio of desired to undesired signal. Connect
one input to a source containing both the
desired and undesired signal.
remaining input to a source containing
the undesired signal. Place the MODE switch
in the ADDED ALGEBRICALLY position.
the POLARITY switches to opposite polarities
(depending upon the polarity of the desired
not
signal). By careful adjustment, especially at
low frequencies, of the VARIABLE
and/or the GAIN ADJ. controls the amplitude
of the undesired signal displayed can
by a factor of 20 compared to the amplitude
of the desired signal.
Note
displayed
up being the
This
two
apart.
will be con ­
waveforms
cycle. Tran ­
1 msec duration can be
about 100 elements in
control
to position,
waveforms so they
ALGEBRAICALLY position)
Connect the
controls
be reduced
is
only
et
AA