Tektronix 53C Instruction Manual page 5

Positioning Adjustment
The VERT POS RANGE control balances
the de output level so the full range of the front ­
panel positioning controls can be utilized. This
control is accessible when the left side panel is
removed. Center the trace in both the A ONLY
and B ONLY positions of the MODE switch.
Note the settings of the VERTICAL POSI ­
TION controls. Adjust the VERT POS RANGE
control so both the A-channel and B-channel
VERTICAL POSITION controls are approxi ­
mately centered when the displayed trace is cen ­
tered.
DUAL-TRACE OPERATION
Generally, two types of operation will be per ­
formed using the dual-trace function of the
53/54C; the observation of repetitive waveforms
and the observation of single transients. The
two types of operation are fundamentally differ ­
ent so we will examine them in the order stated.
Repetitive Signals
Connect the two signals to be compared to
the two signal inputs and turn the MODE
switch to A ONLY. Set the sweep up for trig ­
gered operation and adjust the VOLTS/CM
and VERTICAL POSITION controls as neces ­
sary to display the waveform. Turn the MODE
switch to B ONLY and adjust the correspond ­
ing controls as necessary to display the other
waveform. Now turn the MODE switch to
ALTERNATE. If necessary, touch up the oscil ­
loscope ' s sweep triggering controls to obtain a
stable image. Both waveforms will now be dis ­
played on the ert screen. As the control of each
amplifier is independent you can position, atten ­
uate, or invert the signals as necessary to com ­
pare their shape, relative amplitudes, etc.
Use the AC FAST triggering mode and AL ­
TERNATE sweeps for INTernal triggering on
signals having components above 10 kc. For low ­
er-frequency signals, use the AC SLOW trigger ­
ing mode. In the AC FAST position, an rc filter
is inserted into the circuit allowing it to recover
quickly from the de level changes encountered
with the ALTERNATE sweep. To compare the
phase difference between two signals, you should
53/54C — OPERATING INSTRUCTIONS — PAGE 2
trigger externally using the reference signal as
the trigger signal.
Single Transients
When it is necessary to observe a single tran-
ient at two parts of a circuit another 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 at ­
tempted to observe a single transient in this
manner the transient will pass through which ­
ever amplifier happens to be conducting and will
trigger the sweep. This will display the trans ­
ient as seen by whichever amplifier is conduct ­
ing 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 ob ­
serve 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 amplifier
is conducting for about 5 µsec and then is cut off
while the other amplifier conducts for an equal
length of time. In this case the sweep is being
triggered by the switching waveform, particu ­
larly if the two traces are positioned very far
apart, as the switching waveform is equivalent
to a 100-kc square wave. It will usually be very
difficult if not impossible to trigger the sweep
internally from the signal so the sweep controls
should be set for external triggering. Review
the OPERATING INSTRUCTIONS section
of the oscilloscope ' s instruction manual for the
proper procedure for external triggering of the
sweep.
Now the two signals to be observed can be
connected to the two inputs and both wave ­
forms will be displayed during one sweep cycle.
Transients as short as 1 msec duration can be
well delineated, with about 100 elements in each
trace. As before, the independent control of
each amplifier will allow you to position, attenu ­
ate, or invert the waveforms so they can be
easily compared.