Example: Taking Tdr Measurements; Figure 3 95: Connections For Example - Tektronix 11801C User Manual

TDR
Example: Taking TDR
Measurements
3 194
This example demonstrates the TDR (Time Domain Reflectometry) feature of
the SD 24 sampling head. TDR is a method of examining and measuring a
network or transmission line by sending a step into the network and moni
toring the reflections.
For this example you will need an 11801C with at least one SD 24 installed.
Also, you will need one SMA cable, preferably of 5 ns length.
Step 1: Initialize the 11801C (press UTILITY, touch Initialize and touch
Initialize again).
Step 2: Attach one end of the cable to any SD 24 sampling head input.
Leave the other end unattached.

Figure 3 95: Connections for Example

Step 3: Press the SELECT CHANNEL button on the sampling head
input channel to which you have connected the cable.
You see only a flat trace on the display because there is no signal on the
channel. But, when the TDR feature is used, the sampling head supplies the
signal for you. As with the calibrator signal, the TDR step is synchronized
with the internal clock.
Step 4: Press the WAVEFORM button, and touch the Sampling Head
Fnc's selector.
Step 5: To turn on TDR, touch TDR Preset. The TDR Preset function
acts to turn on the step generator for the selected channel, creates a
trace from that channel, sets the graticule to rho scaling, turns on base
line correction, and autosets the TDR waveform.
The sampling head will turn on a red light next to the channel input connec
tor, indicating that TDR is activated for that channel. TDR can be used on
each channel independently.
Step 6: Adjust the display sizes and positions to show a trace similar to
that shown in Figure 3 96. AUTOSET may make this job easier, and the
vertical ( ) and horizontal (
ments.
) icons will let you make fine adjust
Not
Connected
Reference