Operator Tutorial
1502C MTDR User Manual 2–5
The Waveform Up Close
It helps to know what makes up a pulse. Here is the waveform anatomy using the
3-foot test cable as an example:
1. Turn the
n
o
POSITION control counterclockwise until the distance window
reads –2.000 ft. The cursor will be on the far left side of the display and the
reflected pulse will be near center.
2. Set the 1502C front-panel controls:
CABLE 3-ft test cable, no short
NOISE FILTER 1 avg
VERT SCALE 500 mr
DIST/DIV 1 ft (0.25 m)
Vp .66
3. The first (left) step is the incident pulse, as sent from the pulse generator (see
Figure 2–5). The second step is the reflected pulse, as it bounces back from
the end of the cable. The reflected pulse and the time between pulses
provides the information needed for calculating the distance between faults
or the end of the cable.
O
F
F
O
F
F
O
F
F
O
N
ac –2.000 ft
Reflected
Pulse
Incident
Pulse
Figure 2–5: 3-foot Cable with Cursor at Far Left
4. Adjust the
n
o
POSITION control so the cursor is at the beginning of the rise
of the incident pulse. Note the distance window reads approximately
–0.520 ft. This is the distance from the front panel BNC connector to the
pulse generator circuit board inside the instrument (where the test pulse in
generated).