ECE 488: RF Circuits and Systems Spring 2005
CORNELL UNIVERSITY © WES SWARTZ (03/8/2)
3
The
CH 1 MENU
and
CH 2 MENU
pushbuttons cause the appropriate input channel menu
functions to appear on the side-screen menu and can toggle the channel trace on and off.
3. Horizontal controls
The horizontal position and scaling of the waveform traces are
controlled by the two knobs shown in Figure 4. The
POSITION
knob moves the traces left and right on the screen. The
SEC/DIV
(seconds per division) knob sets the time interval
between each major grid division (approximately one
centimeter) along the horizontal axis of the display. This time
interval is common to all channels currently being displayed. It
is adjustable from 5 nanoseconds to 5 seconds per division.
Finally, the
HORIZONTAL MENU
button selects additional
horizontal functions for the side-screen menu.
Warning 1: It is entirely possible to move the traces completely
off the screen with the POSITION knob.
Warning 2: Since this is a “sampling” scope, make sure that
the time base is properly set to avoid aliasing of high frequency
signals.
4. Trigger controls
Triggering determines when the painting of a trace across the display
begins. Triggering can be automatic or forced manually depending
on the settings of these controls. Triggering can be repetitive (for
periodic waveforms) or produce just a single sweep for single events.
Automatic triggering begins when the input voltage crosses a selected
voltage level (determined by the
LEVEL
knob) in the selected
direction (either increasing or decreasing as determined by the
RISING
EDGE/FALLING EDGE
item in the side-screen menu selected by the
TRIGGER MENU
button). The input voltage used to cause triggering
can be either of the input channel signals (
CH 1
or
CH 2
BNC input
connectors) or a special signal delivered to the
EXT TRIG
input BNC.
The triggering signal can be shown on the display by pushing and
holding the
TRIGGER VIEW
button. Improper setting of the trigger
controls can result in an overlay of confusing multiple traces, or no
trace at all. A wonderful feature of the TDS 220 is the automatic
setup feature initiated by the
AUTOSET
button (see Figure 1).
Figure 4: Horizontal
Controls.
Figure 5:
Trigger
Controls
