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Time Domain Reflectometry (TDR) Technology
In Case of Unstable or Unusual Readings
Sometimes, devices connected to the cable you are testing
can prevent the TS90 from making a valid reading. Such
devices include telephones, fax machines, modems, speakers,
transformers, light bulbs, televisions, and dc loads. The
software makes the best decisions it can when faced with
unusual conditions, but may not always be able to ignore
connected devices. If you get a highly unstable or clearly
invalid reading, check for devices connected to the cable.
Time Domain Reflectometry (TDR)
Technology
Note
This section goes deeper into the theory of
operation. You can skip this section and still use the
tester effectively by reading the other parts of this
manual. However, it is worth reading this section if
you want more insight into how the tester works.
One of the keys to understanding how the tester works is to
first understand that a pair of wires has a fixed impedance as
long as the wires of the pair are kept in the same
geometrical relationship to each other.
A pair of wires (either standalone or within a multi-wire
cable) is designed to have a constant wire-to-wire
impedance. If the physical relationship of the wires in the
pair is altered during the wire run, then there will be a
change in impedance at the point where the physical
relationship changes.
