Introduction - Megger TDR1000 Manuel Utilisateur

Introduction

Thank you for purchasing this quality AVO product. Before using your new instrument please take the time to read
this user guide, ultimately this will save you time, advise you of any precautions you need to take and could
prevent damage to yourself and the instrument.
The MEGGER TDR1000 is an advanced instrument capable of identifying a wide range of cable faults. The
instrument uses a technique called Time Domain Reflectometry (TDR) which in many ways is similar to radar.
Narrow pulses of electrical energy are transmitted along a pair of conductors in a cable. The pulse travels through
the cable at a velocity determined by the insulation between the conductors and this resistance to the flow of the
pulse is characterised as impedance for the cable. Changes in cable impedance will cause a proportion of the
pulse to be reflected. The pulse velocity is normally described as a fraction of the speed of light and is called the
Velocity Factor. By measuring the time between the transmitted pulse and the reception of the reflected pulse,
and multiplying this by the speed of light and the velocity factor, the actual distance to the reflection point can be
given.
Faulty cables, poor joints or discontinuities will all cause a change in impedance. Impedance's higher than the
cable's cause a normal reflection; Impedance's lower than the cable's cause an inverse reflection. Matched
terminations absorb all the pulse hence no reflection will occur, the cable appearing endless. Open or Short
circuits will reflect all the pulse energy and the TDR will not 'see' the cable beyond that fault.
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