3M 965AMS User Manual

Use the Time Domain Reflectometer (TDR) 

 function to 

map the high-frequency impedance of the cable along its length. 

The display shows opens, load coils, splits, wet sections, splices, 

gauge changes, heavy shorts and any other physical deviation 

from a perfect cable. Each of these events have their own unique 

signature. A user-controlled vertical cursor is used to measure 

the distance to an event.

“Events” are the “dips” and “peaks” seen on the screen caused 

by faults or changes in the pair.

“Peak” Events
1.  Launch Pulse: The first peak on the screen is the “launch 

pulse” which occurs where the transition from the tester to 

the test leads occurs.

2.  Open: A clean or partial open will show up as a peak on 

the screen. The “cleaner” the open, the taller the peak. A 

complete open will be the tallest peak (other than the launch 

pulse).You can not see events past a complete open.

3.  Load Coil: A load coil looks very similar to an open. If 

you think there is a load coil on the pair, use the Load Coil 

function (in the POTS test) to verify its presence. You can 

not see events past a traditional load coil.