Megger TDR1000/2 Guia Del Usuario página 11

Operation
If no significant reflections can be seen use the "TX
Null" to minimise the effect of the output pulse on
any potential "near end" faults (refer to section
on TX Null).
In the event of no reflections being visible, increase
gain until any reflection can be easily identified.
(If no reflections can be seen, try shorting or
earthing the far end of the cable to ensure that
you are "seeing" the whole length of the cable).
The cursor can also be moved using the LEFT
and RIGHT cursor keys. Move the cursor to the
beginning of the reflection. The distance to the
fault can then be directly read from the display.
NOTE: The distance calculation is performed using
the velocity factor set in the TDR. If this velocity
factor is not correct for the circuit under test, the
displayed distance will be incorrect.
Opposite are shown two typical trace displays.
The top shows an open circuit at 2000m away; the
second a short circuit at 2000m away.
2000m
3000m
2000m
3000m
100
100
2000m
3000m
2000m
3000m
100
100
0.67R
0.67R
0.67R
0.67R
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