Radiodetection 1205CXA User Manual

4
SECTION 2: OPERATING PROCEDURES
2.1 Theory of Operation
A Time Domain Reflectometer (TDR) works on the
same basic principle as radar. Pulses of energy are
transmitted down the cable under test. If the cable has
a constant impedance and is properly terminated, all
of the energy will be absorbed.
If the pulse reaches an impedance discontinuity,
part or all of the pulse energy is reflected back to the
instrument. If the cable is an open circuit, the reflected
pulse will be in-phase (upward reflection) with the
output pulse. If the cable is a short circuit, the reflected
pulse will be out-of-phase (downward reflection) with
the output pulse.
In either case, a substantial amount of energy will be
reflected. If it were possible to have a cable with no loss,
all of the signal energy would be reflected. The incident
and the reflected signals would look identical.
Reflections from an impedance higher than the char-
acteristic impedance of the cable are in-phase, or
upward. Reflections from an impedance lower than the
characteristic impedance of the cable are out-of-phase,
or downward.
Inductive faults cause the TDR to display an impedance
higher than the characteristic impedance of the cable
being tested. Capacitive faults cause the TDR to display
an impedance lower than the characteristic impedance
of the cable.
The Model 1205CXA displays the cable under test as
a digitized waveform with a numeric distance readout
on the Liquid Crystal Display.
The digitized waveform enables the operator to view the
signature of the cable in great detail. An impedance
mismatch (opens, shorts or faults of less severity) can
be identified and distances to the faults determined.

Radiodetection 1205CXA Specifications

General

Category	Cable and Pipe Locator
IP Rating	IP54
Frequencies	512Hz, 8kHz, 33kHz, 65kHz, 83kHz
Current Measurement Accuracy	±5% (typical)
Operating Temperature	-20°C to +50°C