Tektronix 1503C, Руководство пользователя, Страница: 47 / 128

Operator Tutorial
1503C MTDR User Manual
2–5
2. Set the 1503C front-panel controls:
CABLE 10-ft test cable, no short
IMPEDANCE 93
NOISE FILTER 1 avg
VERT SCALE 0.00 dB
DIST/DIV 1 ft (0.25 m)
Vp .84
PULSE WIDTH 2 ns
3. The first (left) pulse is the incident pulse, as sent from the pulse generator (see
Figure 2–2). The second bump 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.
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 –0.40 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).
O
N
ac –0.40 ft
O
F
F
O
F
F
O
F
F
Figure 2–6: 10-foot Cable with Cursor at Incident Pulse
5. Adjust the VERT SCALE control to approximately 25 dB. Adjust the
n
o
POSITION control to keep the middle portion of the pulse on the display. The
bumps following the incident pulse are the aberrations from the internal
circuitry and reflections between the open end of the cable and the front panel.
O
N
ac –0.40 ft
O
F
F
Figure 2–7: 10-foot Cable with Cursor at Incident Pulse, Vertical Scale at 25 dB