ECE 488: RF Circuits and Systems Spring 2005
CORNELL UNIVERSITY © WES SWARTZ (03/8/2)
2
particular menu was selected by the
CH 1 MENU
button within the Vertical Controls
section. The
DC
coupling mode means that “Direct Current” voltages are fed in (and not
blocked as in
AC
coupling). Higher
frequencies can be
blocked by changing the
BW
(band-width) setting
to
ON
. The
10X
probe
setting means that the
selected probe attenuates
the signal by a factor of
ten and that the readings
on the scope will be
adjusted to compensate
for this factor.
A second example for the
display is shown in
Figure 2. Here the same
pulse-train signal is fed
into both channels. Note
the change in the time
base.
2. Vertical controls
The vertical position and scaling of the traces for the
two channels is controlled by the two sets of knobs
shown in Figure 3. The
POSITION
knobs adjust the
vertical position of the zero voltage level for each
channel. (In extreme positions, the traces can be moved
completely off the display. Beware of this.) The
VOLTS/DIV
(volts-per-division) knobs control the
amount of gain applied to the signals and hence
determine the vertical axis scales of the display. These
values are displayed along the bottom edge of the
screen as mentioned above under the display section.
The probe point is attached to the signal source to be
measured, and the black wire lead is attached to a
suitable ground (usually the ground pin of the same IC
to minimize noise pickup). Try adjusting these knobs
while observing the effects on the display.
Figure 3: Vertical Controls.
Figure 2: Example of a two-trace display on the TDS 220.
