Reference
34 80E00 ElectricalSampling Modules User Manual
Overview Controlelem ents& resources
Totake a common mode or differential TDR
measurement(cont.)
PresetTDR 4. Initializethe instrument (pressDEFAULT SETUP).
5. Pressthe SETUP DI ALOGS button and select the TDR
tab.
6. PressTDR Preset for both channel s (fort he sampling
module connected to the cables) to turn them on. Select
the polarity desired for both channels.
TDRPreset set s Internal Clock in the Trigger menu,
turnson t he TDR Step in the TDR Setups menu, turns
onand sel ects the acquisition Units in the TDR Setups
menu.
Thesam pling module will turn on red lights next to the
SELECTCHANNEL but tons, indicating that TDR is
activated for the channels.
7. Set the scale to ρ.
8. Pressthe SETUP DI ALOGS buttonto dismiss the
dialog box.
TDRtab
Set
units
Enable
TDR
TDR
preset
SetOther TDR
parameters
9. Adjust the Manual Step Deskew adjustment to set the
time at which the step generator for the right channel
assertst he TDR step relative to the left channel. Notice
that the second edge moves horizontally, relative to the
first edge. Adjust the right step generator step to divide
the mismatch between channels equally between the
incident step and the reflections.
10. After dividing the mismatch equally between channels
using Manual Step Deskew, adjust Channel Deskew to
align the front edge of the reflections. (for more
informationsee Adjusting TDR Step Deskew on
page37).
11. Press the SETUP DIALOGS button.
12. Adjust the VERTICAL (2.5 ρin this example) and
HORIZONTALSCALE (2 ns in this example) to show a
tracesimilar to that shown. Leave at least one division
of baseline trace to the left of the first rise.
Thef irst rise of this trace is the incident TDR step
leaving the sampling module; the second rise is the
reflection of the step returning from the end of the cable.
ρ
ρ
Frontedge of reflections
IncidentTDR steps