Tektronix CSA7154, Руководство пользователя

Страница: 98 / 480

Acquiring Waveforms
3- 20
CSA7000 Series, TDS7000 Series, & TDS6000 Series Instruments User Manual
Autoset Considerations. Autoset acquires samples from the input signal and
attempts to take the following actions based on the input data:
H
Evaluate the amplitude range of the input signals and set the size and vertical
offset of the vertical acquisition window to acquire the signal with good
resolution, but without clipping.
H
Set the trigger to the approximate midlevel of the signal being autoset and
switches to edge trigger mode.
H
Evaluate the signal transitions and set the horizontal scale to produce a
waveform display of 2 or 3 cycles of the input signal.
Sometimes Autoset cannot produce a correct display due to the nature of the
input signal; if so, you may have to adjust the scale, trigger, and acquisition
controls manually. Some conditions that can cause Autoset to fail are:
H
No signal present
H
Signals with extreme or variable duty cycles
H
Signals with multiple or unstable signal periods
H
Signals with too low amplitude
H
No recognizable trigger signal
H
Signals with a frequency
<
20 Hz
H
Signals with a frequency above the bandwidth of the instrument
H
Signals with high offset and low peak-to-peak variations
Vertical Acquisition Window Considerations. You can set the vertical size,
position, and offset of each channel independently of other channels. Vertical
scale and offset specify the vertical acquisition window for each channel. Parts of
the signal amplitude that fall within the vertical window are acquired; parts
outside (if any) are not.
The offset control subtracts a constant DC level from the input signal before the
vertical scale factor is applied, and the vertical position control adds a constant
number of divisions of signal after the scale factor is applied to the resulting
difference.