Deskew and Gain Cal Fixture Instructions
12
Deskew Fixture Instructions
Using the Deskew Fixture to deskew channels
You can adjust a relative time delay for each channel. This lets you align the
signals to compensate for signals that can come in from cables of differing
lengths. The oscilloscope’s deskew feature applies deskew values after it
completes each acquisition; therefore, the deskew values do not affect logic
triggering. Also, deskew has no affect on XY and XYZ display formats.
This procedure requires the user to select a common reference channel which all
other channels will be deskewed. This is typically Channel 1, but can vary
depending on the user’s setup.
For best results warm up the oscilloscope for 20 minutes before performing these
functions.
1.
Connect the probes to the oscilloscope.
When the probes are inserted properly with both tips contacting the correct pins,
you will see the following approximate squarewave amplitude: 1500 mV for
differential probes; 750 mV for single-ended probes. If you do not see this
approximate amplitude, remove the probe and reinsert it or adjust it until the
approximate amplitude is achieved. Then, continue with the deskew process.
2.
Touch the
Vertical
menu to display the
Deskew
menu.
3.
Select Channel
1
and set the Deskew to
0.0s.
4.
Display all channels that you want to deskew, including the reference
channel.
5.
Push the
AUTOSET
button on the oscilloscope.
6.
From the
Horiz/Acq
menu, select
Horizontal/Acquisition Setup
, select
Acquisition
tab, select
Average
and
# of Wfms 16
. Adjust trigger level to
get a stable trigger.
7.
Adjust the vertical
SCALE
and
POSITION
(with active probes adjusting
offset
can be required) for each channel so that the signals overlap and are
centered on screen. It’s advised to make sure all channels being deskewed are
at the same Volts/div setting. See Figure 12 on page 13.
8.
Adjust the horizontal
POSITION
so that a triggered rising edge of the
reference channel is at center screen.
9.
Adjust the horizontal
SCALE
so that the differences in the channel delays
are clearly visible.
10.
Adjust the horizontal
POSITION
again so that the reference channel’s first
rising edge is at center screen.
