Channel Operation - Tektronix 1A2 Instruction Manual

Operating Instructions—Type 1A2
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Fig. 2-4. Probe compensation waveforms using 1-kHz calibrator signals.
if the setting of this control is moved away from the CALI-
BRATED position.
The range of the VARIABLE control is at least 2.5 to 1
to provide continuously variable (uncalibrated) vertical deflec-
tion factors between all calibrated settings of the VOLTS/
CM switch. When the control is turned to its maximum-
counterclockwise position and the VOLTS/CM switch is set
to 20, the VARIABLE control extends the vertical deflection
factor to about 50 volts/cm. By applying the oscilloscope
calibrator voltage or any other calibrated voltage source to
the Type 1A2, any specific deflection factor can be set within
the range of the VARIABLE control.
PULL TO INVERT Switch
The PULL TO INVERT switch may be used to invert the
displayed waveform, particularly when using the dual-trace
feature of the Type 1A2. The PULL TO INVERT switch has
two positions. With the knob pushed in, the displayed wave-
form will have the same polarity as the applied signal; that
is, @ positive-going pulse applied to the Type 1A2 will be
displayed as a positive-going waveform on the CRT. If a
positive voltage is DC coupled to the Type 1A2, the beam will
move up.
With the switch pulled the displayed waveform will be
inverted; that is, a positive-going pulse applied to the Type
1A2 will be inverted or displayed as a negative-going wave-
form on the CRT. If a positive voltage is DC coupled to the
Type 1A2, the beam will move down.
MODE Switch
The MODE switch has five positions: ALT, CH 1, ADD,
CH 2, and CHOP. These positions and their purposes are
described in subsequent paragraphs. Useful triggering inform-
ation is included in the description of the ALT and CHOP
switch positions.
CH 1, CH 2—Single Channel Operation
To display a single signal (single-channel operation), apply
the signal either to the Channel 1 or Channel 2 Input con-
nector and set the MODE switch to the corresponding posi-
tion: CH 1 (Channel 1) or CH 2 (Channel 2).
To display a signal in one channel independently when
the same signal or a different signal is applied to the other
channel, simply select the signal in the channel to be dis-
played by setting the MODE switch to the appropriate CH 1
or CH 2 position.
ALT, CHOP—Dual Trace Operation
To display two signals together (dual-trace operation),
apply one signal to the INPUT 1 connector and apply the
other signal to the INPUT 2 connector.
In general, use the CHOP position (chopped-mode opera-
tion) with sweep rates of 50 usec/cm or slower for displaying
two non-repetitive signals occurring within the sweep-time
interval set by the oscilloscope Time/Cm switch. Non-repeti-
tive signals are those signals which are transient or random.
The CHOP position is also useful for displaying low-frequency
synchronous signals. Synchronous signals are those which
have the same repetition rate or are frequency-related by
whole number multiple.
NOTE
When using chopped-mode operation, be sure to
set the oscilloscope CRT Cathode Selector switch
to the Dual-Trace Chopped Blanking position to
blank out the undesirable chopped-mode switching
transients.
Use the ALT position (alternate-mode operation) when
using sweep rates at about 0.5ms/cm or faster to display
high-frequency synchronous and asynchronous signals. Asyn-
chronous signals are those which do not have the same repeti-
tion rate or are not frequency related to each other by a
whole number multiple. Table 2-2 summarizes the following
discussion for dual-trace operation.
Displaying Two Non-repetitive or Low-Frequency
(Below 2 kHz) Synchronous Signals. To show true time
and phase relationship between two non-repetitive or low-
frequency synchronous signals, use chopped-mode operation.
Transients as short as 0.5ms can be well delineated or
resolved. At 50 us/cm a 0.5 ms duration transient, for exam-
ple, will contain about 200 on segments in the trace. If a
higher sweep rate is used, the number of segments that make
up each of the traces will be less and therefore resolution will
be poorer.
2-5