Megger CFL510F Operating Manual

M

CFL510F
Cable Fault Locator

USER MANUAL

GSAFETY WARNINGS

Although this tester does not generate any hazardous voltages, circuits to which it can be connected could be
dangerous due to electric shock hazard or due to arcing (initiated by short circuit). While every effort has been
made by the manufacturer to reduce the hazard, the

user must assume responsibility for ensuring his, or her

own safety.
For use on energised systems rated up to 300 V Installation Category III* the fused clip set Megger Part

Number 6111-218, must be used.

* Relates to the transient over voltages likely to be met in fixed wiring installations.

4mm plug to BNC Adaptor:

This 4mm plug to BNC adapter is intended for use with telecomm network cables only, it is not designed or
intended for direct connection to an energised mains supply. However, in normal use it may be subject to telecom
network voltages (TNV) as defined by IEC 60950 3rd edition (1999-04).

The BNC plug and socket are, by necessity, accessible. The outer sheath for this connector is normally at SELV
levels, however under single fault conditions it may carry hazardous voltages. The operator must therefore verify
that the accessible plug or socket is at SELV levels prior to touching, or alternatively wear appropriate insulated
gloves.

■ The instrument should not be used if any part of it is damaged.

■ Test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked

insulation.

■ Check that all lead connections are correct before making a test.

■ A Fused Lead Set must be used to connect to energised live systems. Refer to the accessories section for options.

■ Disconnect the test leads before accessing the battery compartment.

■ Refer to operating instructions for further explanation and precautions.

■ Safety Warnings and Precautions must be read and understood before the instrument is used.

They must be observed during use.

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NOTE

THE INSTRUMENTS MUST ONLY BE USED BY SUITABLY TRAINED AND COMPETENT PERSONS.

CONTENTS

3

GSafety Warnings 3

Introduction 5

General description
Battery replacement

User Controls and Display 8

Layout and functions

Operation 10

General Testing procedure
Line Feed
Connection to cable under test
Measuring distance to fault
Menu
TX Null
Velocity Factor
Pulse widths
Techniques to improve accuracy

Care and Maintenance 15

Specifications 16

Symbols used on the instrument are:

G Caution: Refer to accompanying notes.
F Equipment protected throughout by

double or reinforced insulation.

t Instrument flash tested to 3.7kV rms.
c Equipment complies with current EU

directives.

INTRODUCTION

Thank you for purchasing the CFL510F cable fault
locator. Before attempting use of 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 CFL510F is an advanced instrument capable of
identifying a wide range of cable faults. The
instrument uses a technique called Pulse Echo (also
known as Time Domain Reflectometry or TDR). A
pulse is launched into a cable from one end. This can
be on either a pair of conductors, or a conductor and
the screen. The pulse travels down 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.
Any 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 established.

Reflections are caused by changes in the cables
characteristic impedance, such as poor joints or
discontinuities. Faults showing an impedance higher

than that of the cables normal impedance will cause
a reflection of the same polarity, i.e.positive, whilst
faults with an impedance lower than that of the cable
will cause an inverse negative going reflection.
Matched cable terminations absorb all the pulse
hence no “end of cable” reflection will occur, the
cable appearing endless. Open or short circuits will
reflect all the pulse and a large reflection will be
displayed. At an open or short circuit all the
transmitted energy is reflected and the CFL510F will
not ‘see’ the cable beyond that fault.

As a pulse travels down a cable, the size and shape
of that pulse is gradually attenuated by the cable. The
pulse reduces in amplitude and becomes more
elongated or stretched. The level of attenuation (or
losses) is determined by the cable type, the condition
of the cable and any connections along its length.
The limit of how far you can see is determined by
the point beyond which you will not be able to see
or distinguish a reflection. To help identify small
reflections, especially at greater distance the CFL510F
has an adjustable gain setting. By increasing the gain
small reflections become more obvious.

The CFL510F can be used on any cable consisting of
at least two insulated metallic elements, one of which
may be the armouring or screen of the cable. The
CFL510F has internal matching networks to allow
testing of 25, 50, 75 and 100 cables. (These typically
correspond to power, coaxial data and data/telecoms

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cable). By selecting the CFL510F impedance closest to
that of the cable under test, maximum power can be
transmitted into the cable allowing long cables to be
tested.

The velocity factor of the CFL510F must be adjusted
to match that of the cable under test, allowing an
accurate distance measurement to be read directly
from the instrument. Where the VF of a cable is not
known, but the length is, the cursor can be set to the
end of the cable and the VF on the CFL510F adjusted
until the correct cable length is displayed.

Other configuration settings include changing the
distance units between metres and feet, changing the
propagation velocity units between a ratio and a
distance per microsecond. Display contrast is fully
adjustable to compensate for all viewing conditions. A
backlight aids viewing in low ambient light
conditions.

The instrument can be powered by manganese-alkali,
nickel-cadmium or nickel-metal-hydride batteries. All
cells must be of the same type.

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When the low battery symbol appears in the
display window the cells are nearly exhausted and
should be replaced as soon as possible. Use alkaline
cells IEC LR6 (AA) 1.5V or 1.2V rechargeable cells
only.

To install or replace the cells, switch the instrument
off. Disconnect the test leads, loosen the battery
cover retaining screws and remove the cover. Lift out
and disconnect the battery holder.

Replace the cells, ensuring that correct polarity is
observed (shown on the battery holder).

Incorrect battery cell polarity can cause electrolyte
leakage resulting in damage to the instrument

Refitting the battery holder is the reverse of removing
it.

BATTERY FITTING AND REPLACEMENT

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