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Instruction Manual
Kommunikationsnetze
Communication
Networks
Elektrizitätsnetze
Pow
er Networks
Rohrleitungsnetze
Water
Networks
Leitungsortung
Line
Location
- Date of release:
2003/34
Mess- und Ortungstechnik
Measuring and Locating Techniques
Easyflex Com
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Easyflex Com
compact and light-weight
Time-Domain Reflectometer
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TABLE OF CONTENTS
1 GENERAL ..................................................................................... 9
1.1 Advice from Hagenuk KMT GmbH.........................................................9
1.2 Terms and conditions of warranty........................................................10
1.3 Safety Instructions................................................................................11
1.4 Indications used in the description.......................................................12
2 TECHNICAL DESCRIPTION....................................................... 13
2.1 General Description..............................................................................13
2.2 Specifications........................................................................................15
2.3 Items Supplied and Optional Extras.....................................................19
3 OPERATION................................................................................ 21
3.1 Measuring Terminals............................................................................21
3.2 Display..................................................................................................22
3.3 Functions of Keys and Rotary Encoder................................................24
3.4 Getting Started (Insert / Replace Accumulator) ...................................27
3.5 Switching On and Off............................................................................27
3.6 Main Menu............................................................................................28
3.7 Compensation of Initial Reflection........................................................28
3.8 How to Locate a Fault...........................................................................29
3.8.1 Fields of Application ..........................................................................30
3.8.1.1 Faults Causing a Negative Reflection.....................................30
3.8.1.2 Faults Causing a Positive Reflection.......................................31
3.8.1.3 Further Fields of Application ...................................................32
3.8.2 Testing a Cable with Known Nominal Velocity of Propagation NVP or
with Known Pulse Propagation Velocity (v/2)..............................................33
3.8.3 How to Determine an Unknown Nominal Velocity of Propagation or
Pulse Propagation Velocity.........................................................................35
3.8.4 Simplification of Fault Location Using Comparative Tests................35
3.8.5 Averaging...........................................................................................36
3.8.6 Mode NEXT.......................................................................................37
3.8.7 How to Use the Marker......................................................................38
3.8.8 Change of Pulse Width......................................................................39
3.8.9 Self Test.............................................................................................40
3.9 Memory Function..................................................................................41
3.10 Serial Interface ...................................................................................43
4 NIMH ACCUMULATOR CHARGER ........................................... 44
4.1 Technical Description...........................................................................44
4.1.1 Specification ......................................................................................44
4.1.2 Start-Up .............................................................................................45
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4.1.3 General Instructions on How to Handle a NiMH Accumulator ..........46
4.2 Operation..............................................................................................47
4.2.1 Safety Precautions.............................................................................47
4.2.2 Modes of Operation...........................................................................47
4.2.3 Practical Hints....................................................................................48
4.3 Troubleshooting....................................................................................49
5 CARE UND MAINTENANCE.......................................................49
6 APPENDIX...................................................................................50
6.1 List of Abbreviations Used....................................................................50
6.2 Conversion: NVP ⇔ v/2.........................................................................51
6.3 Table: NVP and v/2 for Common Types of Cables................................52
6.4 Glossary................................................................................................54
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EC - Declaration of Conformity
CE Mark
We, the company Hagenuk KMT
Kabelmesstechnik GmbH
Roederaue
D-01471 Radeburg
Germany
declare under sole responsibility that our product
Easyflex Com
is in conformity with the directive of the Council of European Communities for
the Harmonization of the Laws of Member States on Electromagnetic
Compatibility (EMC Directive 89/336/EEC) and Low Voltage (Directive
73/23/EEC).
This EC Declaration of Conformity is the result of a verification test performed
by the department of Quality Assurance of Hagenuk KMT Kabelmesstechnik
GmbH.
Conformance with the directive on Electromagnetic Compatibility was verified
in accordance with the following standards:
EN 50081 Interference Emission, EN 50082 Interference Immunity
EN 55011 Product Standard, EN 61000-4-2 Electrostatic Discharge, and
EN 61000-4-4 Fast Interfering Electrical Transients
Conformance with the directive on Low Voltage was verified in accordance
with the following standards:
EN 61010-1 Safety Regulations for Electrical Measuring, Control, Regulating,
and Laboratory Instruments and EN 60529 Enclosure Protection
Radeburg, 6th of March 2003
Dr. Iann
Managing Director
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1 GENERAL
1.1 Advice from sebaKMT
This user manual has been conceived as a reference work. It is intended to
help you answer questions and solve problems as quickly as possible.
Should you have any problems, please first read the user manual with
care.
To do this, make use of the index and read the relevant section carefully.
Also check all equipment connections.
If questions still remain unanswered, please contact the following
addresses:
Hagenuk KMT Seba Dynatronic
Kabelmeßtechnik GmbH Meß- und Ortungstechnik GmbH
Roederaue 41 Dr.- Herbert- Iann- Str.6
D - 01471 Radeburg / Dresden D - 96148 Baunach
TELEFON: +49 / 35208 / 84 - 0 TELEFON: +49 / 9544 / 68 - 0
TELEFAX: +49 / 35208 / 84 249 TELEFAX: +49 / 9544 / 22 73
SERVICE-HOTLINE :
TELEFON: +49 / 35208 / 84 211 TELEFON: +49 / 9544 / 68 - 0
TELEFAX : +49 / 35208 / 84 250 TELEFAX: +49 / 9544 / 22 73
e-mail: sales@sebakmt.com
internet: http://www.sebakmt.com
© Hagenuk KMT GmbH
All rights reserved. No part of this manual may be photocopied or
reproduced in any other form without the prior written consent of Hagenuk
KMT. We reserve the right to alter the contents of this manual without prior
notice. Hagenuk KMT shall not be liable for technical or typographical
errors or omissions in this manual. Nor shall Hagenuk KMT accept liability
for damage or injury which is directly or indirectly attributable to the supply,
performance or use of this material.
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1.2 Terms and conditions of warranty
Hagenuk KMT Kabelmesstechnik GmbH will accept a warranty claim
brought forward by a customer for a product sold by Hagenuk KMT under
the terms stated below and the General Terms of Supply of Products and
Services of the Electrotechnical Industries, date of issue May 1993.
Hagenuk KMT guarantees that Hagenuk KMT products are at the time of
their delivery free from defects in workmanship or materials which
substantially reduce their value or serviceableness. This warranty does not
cover faults in supplied software. During the warranty term Hagenuk KMT
will repair defective parts or replace them with new or as-new parts (with
the same operability and service life as new parts) at its option.
Additional warranty claims, in particular claims arising from consequential
loss, cannot be asserted. All parts and products replaced under the terms
of this warranty become the property of Hagenuk KMT.
Warranty claims on Hagenuk KMT lapse 12 months after the delivery date.
Parts supplied by Hagenuk KMT within the framework of the warranty are
also covered by this warranty for the remaining warranty term, but for no
less than 90 days.
Warranty measures are undertaken exclusively through Hagenuk KMT or a
special service shop which is authorized by Hagenuk KMT.
Claims under the terms of this warranty are subject to the buyer notifying
Hagenuk KMT of defects without delay and no later than within 10 days of
the delivery date in the case of perceptible defects.
This warranty does not cover defects or damage caused by the products
being exposed to conditions which are not in accordance with the
specifications, being stored, transported or used incorrectly, or being
serviced or installed by agencies not approved by Hagenuk KMT. The
warranty does not cover damage owing to natural wear and tear, force
majeure or connection to external parts.
Hagenuk KMT is only liable for claims for damages arising from the
violation of claims for repair or replacement in the event of gross
negligence or intent. Any liability for ordinary negligence is ruled out.
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1.3 Safety Instructions
All persons involved in the installation, operation, maintenance and repair
of the Easyflex Com must have read this manual carefully.
The Easyflex Com and its supplementary equipment are in accordance
with the current state of safety technology at the time of delivery. Owing to
the work processes involved, however, there may be parts of the unit and
its peripherals which cannot be given optimum protection without an
unreasonable reduction in function and usability. Good personal safety
practice is therefore indispensable in terms of the protection of staff and the
unit.
Therefore, please comply with the following safety instructions!
GENERAL INSTRUCTIONS
Work on the Easyflex Com and its peripherals must only be carried out by
trained and/or instructed staff. Other persons must be kept away.
This manual must be available for the supervisory, operating and
maintenance staff to refer to.
Improper use may endanger life and limb, the Easyflex Com and
connected equipment, as well as the efficient functioning of the unit
(accident prevention regulations). The Easyflex Com may only be used for
the purpose for which it is intended by the manufacturer.
Always use the correct tools in perfect condition for all work.
Regular checks must be made to ensure that the relevant safety
regulations are being complied with during operation and maintenance.
Never operate the Easyflex Com and its peripherals if they are not in a
technically perfect condition.
Only parts specified by Hagenuk KMT as accessories must be used for the
Easyflex Com and its peripherals, as the necessary safety will not
otherwise be guaranteed. No mode of working which detracts from the
safety of the Easyflex Com must be used.
Replace a accumulator only when the device is switched off and
disconnected.
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The user is under an obligation to report any changes in the Easyflex Com
to the supervisor responsible without delay.
The operator is under an obligation to shut the Easyflex Com down
immediately in the event of a malfunction which detracts from the safety of
staff. The Easyflex Com must only be put back into operation once the
malfunction has been rectified.
ELECTROTECHNICAL INSTRUCTIONS
Connect the Easyflex Com and all its accessories according to instructions
and regulations. Make sure the relevant regulations such as EN, DIN, VDE
or national standards, respectively, are observed.
Repair and maintenance work must only be carried out when the unit is
switched off (dead) and then only by a skilled electrician in accordance with
current accident prevention regulations. A skilled electrician in the sense of
the accident prevention regulations is a person who can assess the work
assigned to him/her and recognise possible dangers on the basis of his/her
technical training, knowledge and experience, and of his/her knowledge of
the relevant regulations.
1.4 Indications used in the description
Important instructions concerning personal protection, work safety and
technical safety are indicated as follows:
CAUTION
Caution indicates work and operating procedures which
must be complied with in full to prevent the Easyflex Com
and/or its peripherals from being damaged or ruined.
NB
NB indicates special technical requirements to which the
user must pay particular attention when using the Easyflex
Com.
Equipment protected by double insulation or reinforced
insulation.
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2 TECHNICAL DESCRIPTION
2.1 General Description
The
Easyflex Com
is a compact, light-weight and easy-to-handle digital
time-domain reflectometer for locating faults in balanced
telecommunication and control lines. It can be handled easily and so
enables even an inexperienced user to locate faults precisely and fast.
Experts in testing will find a variety of additional functions at their hands. By
its design the
Easyflex Com
is a robust device suitable for field application.
The
Easyflex Com
is double-insulated and equipped with safety terminals
to protect the user.
The
Easyflex Com
is similar to radar in that it employs the pulse reflection
technique. Suitable test pulses are transmitted into the cable to be tested.
The pulses travel along the cable at a propagation velocity that is
dependent on the connected test object. In every place where the electric
characteristics of the cable have changed, part of the transmission pulse is
reflected and caused to travel back to the
Easyflex Com
where it will be
displayed on the screen with a time delay corresponding to its propagation
time.
A change in the electric characteristics of a cable may be caused either by
a possible fault or by local circumstances such as junction boxes,
connectors, or the end of the cable. The time delay between the incoming
reflection and the moment of pulse transmission is the propagation time to
the point of fault and back. The distance from a place of interest can be
calculated by taking into account the specific pulse propagation velocity of
the cable under test. Shape and size of the reflected signal allow
conclusion to be drawn on the nature and size of the fault.
The propagation time of the test pulse which is dependent mainly on the
material of cable insulating material is taken into account by specifying a
signal propagation velocity.
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For measuring the distance to the fault, a movable cursor or a combination
of marker and cursor are used. Distance is display in m, ft, or µs as
selected by the user. In order for the distance to be indicated in m or ft, the
pulse propagation velocity of the cable under test has to be entered before
the test is carried out.
The greatest advantage of the pulse reflection method is its ability not only
to find out that there is a fault but also to find its location and type.
The
Easyflex Com
allows two cables under test to be connected to L1 and
L2 at the same time and to show two reflectograms simultaneously. This
can be done using currently taken reflectograms or test results stored in
memory.
The most important modes of testing are:
• Reflection measurement Pair (physical circuit) versus Built-in balancing
network (dummy line)
• Difference measurement of two pairs
• Location of crosstalk (NEXT) Pair versus Pair (k1 measurement)
There are two display modes the user can choose between. When you
wish to get a revealing overview of the cable under test and, at the same
time, have a closer look at a cable section, you can choose the display
mode which divides the screen of the
Easyflex Com
into two windows. The
upper window shows the full distance range with a movable window
marking a section the content of which is displayed zoomed in the lower
window. There is yet another display mode with a full-screen display of the
selected cable section.
Current device settings are display by the LCD. When a stored
reflectogram is uploaded as trace 1, all relevant settings such as gain and
NVP are also taken over from memory thus allowing the current test result
to be easily compared with a reflectogram taken earlier.
The
Easyflex Com
is powered from a NiMH rechargeable accumulator
fitting in a accumulator compartment in the bottom of the unit. The
instrument has a Power-Down mode. Moreover, the unit can also be
powered from an external source of power.
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MAN_Easyflex_com_eng_01.doc 15
2.2 Specifications
Modes of testing:
L1:
Reflection test of cable connected to
socket L1 versus built-in balancing
network
L2: Reflection test of cable connected to
socket L2 versus built-in balancing
network
Alt: A reflection test is carried out alternately on
cables connected to sockets L1 / L2
Diff: Measurement of difference between
cables connected to sockets L1 and L2
NEXT: Location of crosstalk between cables
connected to sockets L1 and L2
Pairs to be connected: 2
Modes of operation:
Single
Cont
Average
Single test
Continuous testing
Averaging of up to 256 test results
Measuring ranges at
v
/2 = 100 m/µs
50, 100, 200, 400, 1000, 2000 m
4, 15 km
Zoom factors (X direction) 1, 2, 5, 10 (depending on range of
measurement)
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Maximum resolution 1.25 cm for range 50 m at 50 m/µs
2.5 cm for range 50 m at 100 m/µs
2.5 cm for range 100 m
5 cm for range 200 m
10 cm for range 400 m
25 cm for range 1000 m
50 cm for range 2000 m
1 m for range 4000 m
2.5 m for range 7500 m
5 m for range 15 km
Accuracy
± 0.1% of range of measurement ± 1
cursor step
Gain 0 … 80 dB in steps of 1 dB
Dynamic range 90 dB
Distance reading m, ft, or µs
Setting range of signal
propagation velocity
NVP
v/2
0.200 … 0.999 in steps of 0.001
30.0 … 149.9 m/µs or
98.4 … 491.8 ft/µs
Pulse amplitude
5 ns 2 V±25 % at 120 Ω
10 ns 2 V±25 % at 120 Ω
20 ns 2 V±25 % at 120 Ω
50 ns 3,5 V−25 % at 120 Ω
200 ns 5,0 V−25 % at 120 Ω
750 ns 6,0 V−25 % at 120 Ω
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Pulse width Pulse width is linked to range of
measurement:
5 ns for range 50 m (100 m/µs)
5 ns for range 100 m
10 ns for range 200 m
20 ns for range 400 m
50 ns for range 1 km
200 ns for range 2 km
200 ns for range 4 km
750 ns for range 7,5 km
750 ns for range 15 km
Electrical strength of test
inputs
250 V AC/DC 50/60 Hz
CAT II (overvoltage category)
Memory locations 16
Measuring rate up to 11 reflectograms per second
(averaging mode, short range)
Display rate up to 4 screen images per second
Display 256 x 128 pixels, back-lighted
Interface RS 232 for PC / printer
Power supply Replaceable NiMH rechargeable
accumulator
(7,2 V/1,7 Ah)
or Plug-in mains unit (optional extra)
Mean operating time with
one accumulator charge
ca. 8 hours
Languages German, English,
other languages as optional extras on
request
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Environmental conditions
Operating temperature -10 °C … +50 °C
Storage temperature -20 °C … +60 °C (without accum ulator)
Storage temperature
(accumulator)
-20 °C … +50 °C
Dimensions, mm 176 x 260 x 70 (L x W x H)
186 x 260 x 70 incl. measuring terminals
Weight approx. 1.5 kg
Interelement protection
class
II with accumulator compartment closed
and protective cap on serial interface
terminal
Enclosure protection IP54
Subject to changes and alterations without further notice!
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2.3 Items Supplied and Optional Extras
Items supplied:
Description
Easyflex Com, consisting of
Easyflex Com
(G,E, two languages on request)
- 2 pcs. set of test leads
- Case for Easyflex Com
- Accumulator 7,2 V / 1,7 Ah / NiMH
- Charge case
- Plug-in mains unit, for charger
case;
according to country:
EURO 230 V / 50 Hz
USA 120 V / 60 Hz
UK 230 V / 50 Hz
- Instruction manual, according to
country:
German
English
More languages on request
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Optional Extras:
Description for use as
Rechargeable accumulator
7,2 V / 1,7 Ah / NiMH
(Energy DC17AA)
replaceable
accumulator
Winkis Com PC software for
evaluating and storing
reflectograms
Printer set means for the on-site
preparation of test
reports
Transportation case for printer set
Plug-in mains unit external source of
power
Adapter cable for charging the
accumulator from a
vehicle electric mains
using the charging
management of the
charger case
Coax adapter for testing coaxial
cables
Fault Converter for locating moisture-
induced faults
Calibration with manufacturer’s test
certificate
Subject to changes and alterations without notice!
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MAN_Easyflex_com_eng_01.doc 21
3 OPERATION
Fig 1
Easyflex Com
, Front View
3.1 Measuring Terminals
L1
In general, these measuring sockets are used for connecting the
faulty line or line to be tested. When using this configuration please
make sure that your
Easyflex Com
is set to mode L1. In mode NEXT
this pair of sockets is used for receiving the crosstalk.
L2
In general, these measuring sockets are used for connecting a
faultless pair of conductors to be used as a reference for comparison
with the test object connected to L1. In mode Diff this facilitates the
detection of small fault reflections in the tested line connected to L1
because each reflection caused by a junction or terminal occurs in
both lines at the same distance and approximately the same size and
will thus almost be cancelled out in the reflectogram due to the
applied method of subtraction. In mode L1, a line that is possibly
connected to L2 will not have any influence whatsoever on the test.
Mode NEXT: This pair of sockets will carry the transmitted pulse.
Mode Alt
: Testing is carried out alternately on L1 and L2.
Mode L2: Reflection measurement of L2
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3.2 Display
The LC-Display has 256 x 128 pixels, controls for setting contrast, and
switchable back lighting. This enables graphic information to be readable
even in difficult lighting conditions.
The activated function is display in representation.
Fig 2 Display
1 Window on display (range/X zoom)
2 Back light
3 Contrast
4 ,M for A loading; -M for D loading
5 Average counter in mode averaging
There are two modes of displaying the reflectograms: Press ”Display” when
you want to work with two images of the trace, see
Fig 3. The upper is the
reflectogram of the full range of measurement. There is a black bar below
this overview indicating a section the position of which can be moved by
means of the cursor. The lower and larger part of the display shows this
black section magnified in full detail.
reflectogram
from memory
∆ distance marker
- cursor
inverted
accumulator condition
or printing is under way
testing
single test /
waiting for
start
no test
Pulse width Line 4 Cursor...m
❄ 1 X-Zoom Mode 5 ∆...m
Gain ...db
Comp ...Ω
Propagation velocity
2 3 2nd
distance from begin
Trace
Range
Y-zoom
NVP; v/2
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MAN_Easyflex_com_eng_01.doc 23
Use the cursor when you want to change the position of the section and
change the X zoom factor when you want to change the width of the
section.
Fig 3: Reflection by the 2 m Interconnect Cable
The LC display will display a warning signal top left when the remaining
charge of the accumulator is insufficient for further operation. Replace the
accumulator or charge it in order to restore readiness for operation. Switch
the instrument off before replacing the accumulator to retain all data.
Press one of the following keys for ca. 1.5 s to return to the default value.
Function
Key(s)
Default value
Cursor Cursor 0.0 m/ft/µs
Gain Gain 0 dB
Compensation Comp
120 Ω
Pulse propagation
velocity
v
/2
NVP
99.9 m/µs or 327.9 ft/µs
or
0.667
Horizontal zoom Zoom 1 (full range)
Mode of connection Line L1
Mode of operation Mode Single
Contrast Light key
(press for 3 sec)
standard contrast
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3.3 Functions of Keys and Rotary Encoder
How to proceed:
• press key(s) to call function
• use rotary encoder for selection
Quick-save operation to memory 1 by 2nd Save and 2nd Recall;
with Alt to memories 1 and 2.
When you press the help key (?) the
Easyflex Com
will display informations
on one of the following topics :
(key ?; select with rotary encoder; press key Mark, key ? for return):
• Information on help
• Fault location
• Operation
• Compensation
• Averaging
• Mode of display
• NVP or v/2
• Types of cables
• Storage
• Device set-up
• Self test (via 2nd Menu)
• Accumulator charging
• DC external
• 2nd keys
On/Off light Save Recall Print Start single test
contrast Stop/Start cont.testing
(hold down key, turn rotary encoder) Stop averagin
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MAN_Easyflex_com_eng_01.doc 25
Marker:
Activate cursor; move
cursor to start point of
measurement; set
marker
Cancel
X-Zoom
Propagation velocity /
NVP
Single or Dual Display
Menu
Menu/Units
Menu/Interface
Menu/Printer
Menu/System
Menu/Power supply
Help
Cursor
Range(Measuring Range)
Gain, dB
Compensation
Modes:
Single
Continuous
Average
Mode of connection:
L1, L2, ALT (alternating)
Diff (Difference L1-L2)
NEXT (cross talk)
Second key functions
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Possible settings in Menu:
Menu/Units Units
NVP units
meter
feet
seconds
NVP
v
/2
Menu/Interface Baud rate
Parity
(Parity bit)
300
1200
9600
19200
None
Even
Odd
Menu/Printer Printer
Layout
HP Deskjet
Epson compatib.
Epson 9 pin
Kodak Diconix
Normal
Special
Menu/System Self test
Date & time
Language
Software version
Serial number
mm.dd.yy / hh:mm:ss /
AM/PM
German
English
2 x other languages
Menu/Power supply Device switched off
Back light switched off
Measurement Rate
Reduction
disabled off; 10 s ...
1200 s
disabled off; 5 s .. 600 s
disabled off; 1 s ... 60 s
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MAN_Easyflex_com_eng_01.doc 27
3.4 Getting Started (Insert / Replace Accumulator)
The accumulator compartment is located in the back of the
Easyflex Com
.
Make sure that all test leads have been disconnected before opening the
accumulator compartment. Switch the device off in order to retain all data.
For inserting or replacing the accumulator open the lid and pull out the
accumulator, if there is one. Insert the charged NiMH replacement
accumulator with its contacts facing the receptacle of the compartment.
Make sure that the accumulator is inserted properly, otherwise you would
be unable to close the lid. Now the
Easyflex Com
is ready for operation.
3.5 Switching On and Off
Press key to switch the
Easyflex Com
on. During run-up the
manufacturer’s logo will be shown for about 2 seconds.
After run-up has been completed, the
Easyflex Com
can be switched off any
time by pressing key . When being switched off the device saves all
device settings, so the same operating status is restored when the
instrument is switched on next time.
The
Easyflex Com
cuts back its function automatically some time after a key
has been pressed last time in order to save accumulator power:
• The device is switched off after 360 sec,
• The back light of the display is switched off after 60 sec,
• The reduction of measuring rate is disabled
These default values as mentioned above can be changed in menu Power
Supply.
Device on/off off 10 sec ... 20 min in steps
of 10 sec
Light on/off off 5 sec ... 10 min in
steps of 5 sec
Meas. rate
reduction
off 1 sec ... 1 min in
steps of 1 sec
Key operations: 2nd; Menu; rotary encoder to Supply menu; Mark; rotary
encoder for Vertical selection; Mark; use rotary encoder to set Time; Mark;
Display
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3.6 Main Menu
Main Menu will appear automatically after the
Easyflex Com
has been
switched on. In this menu measurements are taken employing the device
settings that were in effect when the device was used last time. Most
functions of
Easyflex Com
can be started directly from menu Measurement
by means of the keys or rotary encoder as described in section 3.3.
3.7 Compensation of Initial Reflection
Use key Comp and the rotary encoder to adjust compensation such that
the initial reflection is suppressed on the display. In principle this
adjustment should be made in order to provide for optimum matching of the
Easyflex Com
to the impedance of the respective cable so as to be able to
detect and locate a fault at close range, i.e. at a distance of up to 10
meters.
When a faultless pair of conductors of the same type of cable as the faulty
one is available and when it is connect to sockets L2, the impedance of the
faultless cable is used for reference in mode Diff. In this case
compensation is not operational and matching is guaranteed. Use
compensation when no faultless pair of conductors is available. Switch to
mode L1 or L2 according to the socket pair used and select display mode
”DUAL”. Set cursor to distance zero and adjust compensation such that the
upper image of the reflectogram is displayed as a horizontal line, if
possible, and the initial reflection shown in the lower window of the display
shows as small as possible. For facilitating the setting procedure, first set
gain to 0 dB for coarse balancing and then increase it for doing the fine
adjustment.
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3.8 How to Locate a Fault
When you test a defective cable, always obey by the following basic rules:
(1) Observe the safety precautions given in section 0 without fail.
(2) De-energise the cable to be tested, whenever possible. When you
take measurements on a live line, its voltage must not exceed 250
V AC/DC. In this case do not open the accumulator compartment
and do not remove the cap of the serial interface.
(3) The
Easyflex Com
is able to measure the length of the cable and the
distance to a point of fault. It is not able, however, to find out the route
of the cable between the point of measurement and the location of the
fault.
(4) The precision of the distance reading by the
Easyflex Com
can only be
as good as the precision with which you know the pulse propagation
velocity of the connected cable. In a wet cable the pulse travel time is
increased, so the distance display is too long when the same settings
are used as for a dry cable.
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30 MAN_Easyflex_com_eng_01.doc
3.8.1 Fields of Application
The
Easyflex Com
allows various type of faults to be detected. These are a
few examples:
3.8.1.1 Faults Causing a Negative Reflection
(1) Short circuit: Direct contact of two conductors of a cable. This will
cause a negative reflection, see Fig 4.
Fig 4 Type of Fault Causing a Negative Reflection
(2) Short-circuit to shield: One conductor in a cable is in contact with the
metal shield of the cable. For locating this type of short-circuit, first
disconnect earth from the shield. Then connect the test leads to the
shield and the conductor which is shorted with it.
(3) Reversed (mixed-up) wires: Reversed wires generate a reflectogram
similar to a short circuit but reflections are smaller in size.
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MAN_Easyflex_com_eng_01.doc 31
3.8.1.2 Faults Causing a Positive Reflection
(1) Open circuit: Open circuit means that one or both conductors of a pair
of conductors are broken or have become detached. This will cause a
positive reflection, see Fig 5.
Fig 5 Type of Fault Causing a Positive Reflection
(2) Resistance faults: If a cable is not properly connected in a junction
box, increased contact resistance will occur. This type of fault
generates a positive reflection in a size which is dependent on the
quality of the connection resp. its resistance.
(3) Shield interrupt means that the metal shield of a cable is broken or has
become detached. To locate such faults and to suppress noise signals
on the display, connect the test leads to the shield and to as many
conductors of the cable as possible. This type of fault generates a fault
reflection the size of which is dependent on the resistance of the
interrupt.
(4) Crossed lines (”split pairs”) and restored reversed lines occur when a
telecommunication cable is twisted or untwisted. Usually this may
happen at a cable joint. This phenomenon is one of the main causes
of crosstalk interference. Reversed wires in an untwisted cable will
generate a positive error reflection. If an individual cable is twisted, a
negative error reflection appears. As the distance between the points
of crossing and crossing is usually very small, both reflections occur
almost simultaneously and appear as a single weak reflection.
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32 MAN_Easyflex_com_eng_01.doc
(5) A humidity-induced fault is brought about by water penetrating into a
defective line. At the beginning of a wet section a negative reflection
similar to a short-circuit can be observed, followed at the end of the
wet section by a small positive fault reflection typical of an open cable
end. In some cases, e.g. if the moisture gradually increases or
decreases with distance, these points of reflection spread into a
constant up and down in the horizontal traceform. In an old cable
which is wet along its entire length it may be difficult to detect a
moisture-induced fault because the beginning and the end of the zone
of moisture exposure are not clearly marked. It is only in rare cases
that the fault reflection becomes apparent as clearly as for a shortcircuit or broken line. Moisture in a cable filled with petrolatum may
possibly result in very small fault reflections as the volume of moisture
is only limited.
3.8.1.3 Further Fields of Application
(1) T-joints (Tapped joints) occur when a conductor pair leading to an
extension is tapped off a pair in the main line. Halving the
characteristic impedance at the tap or bridge will result in a fault
similar to a short circuit (negative reflection). The trace on display is
difficult to assess if a pair of conductors is tapped at many points
unless precise information about the structure of the cable network is
available.
(2) Some telephone lines are coil-loaded in order to increase the
inductance of the line and thereby improve the transfer characteristic
of a trunk line. The
Easyflex Com
will interpret the coils used for the
inductive loading of the system as open ends. Connect the instrument
to some point behind the coil if you want to locate a fault which is
situated beyond the bounds of a coil-loaded section.
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MAN_Easyflex_com_eng_01.doc 33
3.8.2 Testing a Cable with Known Nominal Velocity of Propagation
NVP or with Known Pulse Propagation Velocity (v/2)
In many instances the route and characteristics of the cable are known in
which case the nature and position of the fault can located quickly. In such
circumstances proceed as follows:
(1) De-energise or disconnect the Faulty pair and, where appropriate, a
good reference, if possible. When a test has to be performed under
voltage, make sure that the voltage does not exceed ≤ 250 V AC/DC.
(2) Use the test leads supplied with the
Easyflex Com
to connect the
Faulty pair to Line 1 and, when appropriate, the good pair to Line 2.
(3) Press key to switch the
Easyflex Com
on. Menu Measurement will
appear after a few seconds.
(4) Press key (Line) to select the appropriate mode of measurement, e.g.
Diff when a good pair is available or L1 when you test the Faulty pair
alone.
Set to the desired unit of measurement (2nd; Menu; Menu Units),
select a measuring range according to the length of the cable to be
tested, set the pulse velocity to the desired option (NVP, v/2 in m/µs or
ft/µs), set the display mode to ”DUAL ”. The sockets of the instrument
are the zero mark of the cursor. Use the marker to subtract the
supplied interconnect line.
(5) Use keys (v/2) and the rotary encoder to set the cable-specific
propagation time to the value specific value of the cable to be tested.
(6) Match the
Easyflex Com
to the object under test as described in
section 0.
(7) First of all, try to find the (open) end of the cable.
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34 MAN_Easyflex_com_eng_01.doc
(8) Look for a fault reflection in the overview trace displayed on top. In
doing so, increase gain or amplitude correction steadily until the point
of fault is clearly visible.
Fig 6. Display
(9) Use the cursor to move the section marker (black bar between the two
traces) such that the reflection is located above the bar. Then use the
rotary encoder to move the cursor in the lower part of the screen to the
place where the foot point of the fault is located (see Fig. 6).
(10) The distance to the fault can now be read off directly. This value can
be indicated in meters, feet, or nanoseconds depending on the setting
in menu Units. The reflectogram can be saved in a the memory for
documentation purposes .
(11) Press to switch the
Easyflex Com
off after the test has been
completed.
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MAN_Easyflex_com_eng_01.doc 35
3.8.3 How to Determine an Unknown Nominal Velocity of
Propagation or Pulse Propagation Velocity
When the nominal velocity of propagation or pulse propagation velocity of
the faulty cable is not known, a test sample of the same type of cable with
known length is needed (or the distance to a specific point in the cable
must be known).
Set the cursor to the foot point of the known reflection. Then adjust the
NVP or pulse velocity setting such that the indicated distance to the fault
correlates with the actual length of the sample. After that the distance to a
fault reflection in the defective cable can be measured.
3.8.4 Simplification of Fault Location Using Comparative Tests
The reflectogram shown in Fig 6 shows cable and fault in virtually ideal
conditions. In reality, however, there are cable junctions and other
connections resulting in a trace which is normally similar to that shown in
Fig 7 (good pair). In Fig. 8 (Faulty pair), in addition to the fault other cable
reflections are visible which are caused commonly by connections with an
impedance different from that of the line. These jumps in impedance also
appear as reflections and thus render the detection of the reflection caused
by the fault almost impossible. When a multi-pair cable is tested, a
comparative test (see Fig 9) using a good pair (provided that not all
conductors are defective) allows the point of fault to be detected. Connect
the good pair to L2, the faulty pair to L1. Then select mode Alt by pressing
key (Line). Move the cursor to the points where both trace diverge. In Fig
10 mode Diff was used which means that differences between both
reflectograms (fault reflections in the defective cable) occur in places where
the difference on display deviates from the horizontal. Use the cursor to
measure the distance to the foot point of the deviation.
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36 MAN_Easyflex_com_eng_01.doc
Fig. 7 Fig. 8
Fig. 9 Fig. 10
3.8.5 Averaging
Interfering noisy signals may make the location of faults very difficult in
particular when a fault has to be located in a long cable and when high gain
is used. In order to solve this problem, the
Easyflex Com
is equipped with
an averaging mode. Press function key Mode and use the rotary encoder
to enable mode Averaging. The display will display the number of
measurements taken for averaging (max. N256) top right. You can cancel
averaging at any time if the number of measurements taken so far is
sufficient for an efficient interference suppression. Pressing key Start one
more time to start another averaging run.
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MAN_Easyflex_com_eng_01.doc 37
3.8.6 Mode NEXT
Mode NEXT (Near End cross (X) Talk) is for measuring the cross-talk
coupling k1 between two pairs of conductors. Unwanted crosstalk coupling
occurs in particular when wires have been crossed.
The
Easyflex Com
is able to pinpoint the fault precisely, so the fault can
subsequently be eliminated to the point. For instance, the device can
determine the beginning and the end of a ”split pairs” section in a longer
trunk line which is composed of a number of sections.
The point of crosstalk coupling is located as in any normal reflection test.
This mode is different, however, in that the pair which shall carry the
transmitter pulse is connected to L2 and the pair tested for crosstalk to L1.
Press key Line and use the rotary encoder to enable mode NEXT.
Fig. 11
„Split-Pairs“section
Section of line
pair 2
pair 1
L2 L1
Transmission reception
Easyflex Com
Reversed wires crosstalk
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38 MAN_Easyflex_com_eng_01.doc
The direction of the pulse at the beginning of the ”Split Pairs” section may
be positive or negative depending on the direction in which the wires have
been connected to the device. At the end of the ”Split-Pairs” section the
reflection is always inverted as compared with its beginning.
3.8.7 How to Use the Marker
If you use only the cursor you can just determine the distance from the
Easyflex Com
to the point of reflection in the cable. The marker offers you
additional means to set a point of reference in the cable and to take
measurements in relation to this point by means of the cursor. We
recommend to use the marker
• when subtracting the laught of the test leads,
• when the length of a cable section has to be measured (in particular
when a cable is composed of sections with differing NVP / v/2 values),
• for measurements in relation to a known point of reference (this will
increase measuring accuracy), and
• for determining the NVP / v/2 value of a cable section of known length.
Press key Mark to set or erase the marker. To this end press key Cursor
and move the vertical line by means of the rotary encoder to the desired
point of reference. Then press key Mark; the marker will now be displayed
as a vertical dotted line. When you subsequently use the rotary encoder to
move the cursor away from the marked position, the numerical values on
display top right will change. The numerical value behind Cursor indicates
the distance between the output of the
Easyflex Com
and the position of the
cursor whereas the numerical value behind ∆ indicates the distance
between the marked point of reference and the cursor position. Pressing
key Mark one more time will erase the marker. The marker cannot be set to
position 0 m.
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MAN_Easyflex_com_eng_01.doc 39
3.8.8 Change of Pulse Width
Press keys 2nd Range to change pulse width. Doing so will not change the
display range.
Display range
(Range/Zoom at v/2=100
m/µs)
Default pulse width Setting range
5 m 5 ns 5 ns
10 m 5 ns 5, 10 ns
20 m 5 ns 5, 10, 20 ns
50 m 5 ns 5, 10, 20, 50 ns
100 m 5 ns 5, 10, 20, 50 ns
200 m 10 ns 10, 20, 50, 200 ns
400 m 20 ns 20, 50, 200 ns
1 km 50 ns 50, 200, 750 ns
2 km 200 ns 200, 750, 3000 ns
4 km 200 ns 200, 750, 3000 ns
7.5 km 750 ns 750, 3000 ns
15 km 750 ns 750, 3000 ns
The offered combinations of pulse width and display range take into
account that not every pulse width is suitable for every display range. Thus
short pulses are only suitable for testing at close range. On the one hand,
they allow tests to be made with high resolution but they are too heavily
attenuated and spread at longer distance, on the other. Long pulses are
much less attenuated with distance, so clear echos can be received from
distant points. At close range, however, they are inferior to shorter pulses
due to their poor resolution.
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40 MAN_Easyflex_com_eng_01.doc
3.8.9 Self Test
After turn on, the
Easyflex Com
performs an automatic selftest. If error code
1 is display the Lithium accumulator is (almost) discharged (the device will
still operate for a short while, but you should submit it to the Customer
Service to have the Lithium accumulator replaced).
Error code 2 asks for setting the clock (2nd Menu, Menu/System Mark, go
with rotary encoder to Date&Time Mark, select unit of time with rotary
encoder Mark, select unit of time with rotary encoder Mark for return). If
both errors occur at the same time, error code 3 is display.
Key combination (2nd Menu, Menu/System Mark, Self test Mark) starts a
comprehensive self test. Please contact our Customer Service should any
error code be display.
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MAN_Easyflex_com_eng_01.doc 41
3.9 Memory Function
The
Easyflex Com
has 16 memory locations. This is how to save a trace:
• Press key Save
• Use the rotary encoder to select a free memory location or a location
that will be overwritten. The selected memory location is displayed in
inverted mode
• Press key Mark
The memory window will display location number, date and time of
measurement, and parameter Range of the stored reflectogram. Parameter
Range is display according to the value of v/2 or NVP which is currently set.
This has the consequence that any change of the v/2 setting will also
change this value in the reflectogram. When a trace is loaded, v/2 is re-set
to its stored value. In mode ALT two adjacent memory locations are made
available for storage. Memory location 1 is for quick saving triggered by key
combination 2nd Save. If mode ALT is set, quick saving will use memories
1 and 2. For this reason we suggest not to use memory locations 1 and 2
for any reflectograms which shall be retained in memory for a longer period
of time.
This is how a reflectogram is loaded from memory:
• Press key Recall
• Use rotary encoder to select memory location. The selected location is
display in inverted mode.
• Press key Mark
• Use rotary encoder to toggle between loading, A loading, and D loading
• Press key Mark
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Mode of
loading
Mode of display Indication
Loading Reflectogram stored in selected memory
location
A loading The reflectogram from memory is shown as a
dotted line, the reflectogram currently taken is
shown as a continuous line.
If you wish to erase the display of the trace
stored in memory, do so by using the key
combination Recall set rotary encoder to
Erase 2nd trace Mark.
,M top right in
front of Cursor
D loading Difference between current reflectogram and
reflectogram from memory
If you wish to return to the display of the
current reflectogram, do so by using the key
combination Recall set rotary encoder to
Erase 2nd trace Mark.
-M top right in
front of Cursor
Use key combination 2nd Recall for a quick download of a trace from
memory location 1.
The traces stored in memory can later be used for processing or for
printing out a hardcopy. It is also possible, however, to upload them to a
PC using the PC software program
Winkis Com
which is available as an
optional extra. For printing out a reflectogram it is important first to use
Recall to load the trace from memory before pressing key Print. Another
benefit of the memory mode is that it simplifies fault locating and diagnosis.
When a number of test objects with identical cable characteristics are
tested, the entire test set-up can be taken over from a reflectogram already
stored in a memory location, so fault locating can be started without any
delay. The memory mode also allows a current reflectogram to be
compared with up to 16 reflectograms stored in memory.
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MAN_Easyflex_com_eng_01.doc 43
3.10 Serial Interface
The serial interface of the
Easyflex Com
allows reflectograms to be loaded
to an external PC or to connect a printer for printing out a hardcopy. Go to
Menu/Printer to choose from HP Deskjet, Epson combatib., Epson 9 pin,
and Kodak Diconix. The Print function enables the current content of the
display to be printed by the connected printer. Moreover, the trace just
loaded can be transferred to a PC for storing and documentation purposes
provided the communication software
Winkis Com
which is available as an
optional extra is installed on the PC.
Winkis Com
can also be used for re-
loading a reflectogram including its set-up. Furthermore
Winkis Com
gives
you access to all reflectograms stored. Please refer to the software manual
if you wish to learn some more details.
The default configuration of the
Easyflex Com
serial interface
is as follows:
Baud rate 9600, 8 data bits, no parity, 1 stop bit
Part of the set-up can be set in Menu/Interface.
Pin assignment of the interface cable:
Easyflex Com Printer/PC
9 pins 25 pins
RX Pin 2 ←→ Pin 2 TX
TX Pin 3 ←→ Pin 3 RX
GND Pin 5 ←→ Pin 7 GND
ATTENTION
Always cover the 9-pin connector of the
Easyflex Com
with its protective cap when it is not in use. Make
absolutely sure that all test cables have been
removed when the serial interface is being used!
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44 MAN_Easyflex_com_eng_01.doc
4 NIMH ACCUMULATOR CHARGER
4.1 Technical Description
4.1.1 Specification
Plug-in mains unit (Euro, USA, UK):
Input voltage
EURO
USA
UK
230 VAC , ±10 %, 50 Hz
120 VAC , ±10 %, 60 Hz
230 VAC , ±10 %, 50 Hz
Power consumption
EURO and UK
USA
13.8 VA
14.5 VA
Output voltage 12 V DC
Interelement protection class II
Operating temperature range 0 … 40 °C
Storage temperature range -40 … 70 °C
Charger:
Input voltage 12.,0 V DC
Maximum input current 580 mA
Interelement protection class III
Operating temperature range 0 … 50 °C
Storage temperature range -40 … 70 °C
Type of accumulator Replaceable NiMH rechargeable
accumulator 7,2 V (Energy
DC17AA)
Vehicle adapter cable
ATTENTION
The charger, including the mains unit, is only for
use indoor use!
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MAN_Easyflex_com_eng_01.doc 45
4.1.2 Start-Up
First connect the cable from the plug-in mains unit to the DC-IN 12 V
socket of the charger, and only then plug the mains unit into a mains outlet
(see Fig 13).
The green LED of the charger case should now be on continuously, while
the amber LED should flash up at regular intervals.
Now insert the appropriate NiMH rechargeable accumulator into the
charger case until it engages gently.
Please make sure that the accumulator contacts face the direction of the
LEDs because this is the only way contact is made to the electronic
charger circuit (see enlarged details).
The amber indicator lamp shall light up continuously after the accumulator
has been inserted. If it does not, shortly disconnect the charger from the
mains.
After charging has been completed (approx. 3.5 hours), the amber LED will
flash again. You may now remove the accumulator or leave it in the
charger.
Disconnect the charger from the mains whenever you intend not to use it
for an extended period of time. To do so, just unplug the mains unit from
the mains outlet - you need not disconnect the cable from the mains unit to
the DC-IN 12V socket of the charger. We suggest to install the charger
close to an easily accessible mains outlet.
Charger case
Plug-in mains unit
DC-IN 12 V
mains
Fig 12 Connection to a Mains Outlet
green
and
amber
LEDs
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46 MAN_Easyflex_com_eng_01.doc
The accumulator can also be charged from the on-board network of a
vehicle. To do this, use the vehicle adapter cable to connect the charger
case to the 12 V DC on-board network.
Motorcar adapter cable
Charger case
12 V supply
DC-IN 12 V
Fig 13 Connection to a Vehicle supply
Fig 14 How to Insert the NiMH accumulator into the Charger Case
4.1.3 General Instructions on How to Handle a NiMH Accumulator
ATTENTION
Do not short-circuit a accumulator.
Do not dismanntle or modify a accumulator. Do not
dispose of in fire.
Protect batteries from moisture.
Do not expose batteries to strong impacts.
Make sure that a damaged accumulator is disposed of
immediately and properly.
NOTE
A NiMH accumulator may heat up when being charged
or discharged. This is normal and does not indicate a
defect.
Dispose of batteries which cannot be used any longer
properly or submit it for RECYCLING.
Light-emitting diodes
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MAN_Easyflex_com_eng_01.doc 47
4.2 Operation
4.2.1 Safety Precautions
Protect the device from moisture.
Do not cover the ventilation slots of the plug-in mains unit.
Do not insert any items into the ventilation slots.
Never expose to direct heat or direct sunlight.
Do not open the device as there are no user-maintained components
inside and any warranty might be invalidated.
Do not store or use charger and mains unit in the close vicinity of storage
media.
Only use the plug-in mains unit supplied.
4.2.2 Modes of Operation
OPERATION
The green LED is alight.
Indicates that the charger is ready for use.
STATUS / Waiting mode
The amber LED is flashing regularly.
1.) No accumulator has been inserted:
The device is waiting for a accumulator to be inserted for charging.
2.) A accumulator has been inserted:
The accumulator is fully charged and waiting for being removed.
STATUS / Charging
The amber LED is permanently alight.
A accumulator has been inserted. It is being charged.
Please pay also attention to section 4.3, to extend the service life
of the NiMH accumulator.
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48 MAN_Easyflex_com_eng_01.doc
4.2.3 Practical Hints
In order not to reduce the service life of a NiMH accumulator unnecessarily,
make sure that the accumulator is at room temperature when charging is
started.
"Overnight charging" will not cause any trouble since an intact accumulator
cannot be overcharged. Once charging has been completed, the device will
change over to trickle charging to compensate for natural self-discharge.
The optimum way of operation is to have two accumulators, with one
remaining in the charger while the other one is used for powering the
Easyflex Com
.
The charger and the inserted accumulator will heat up during charging
(hand hot). This is normal and does not indicate any defect.
When the operating life of a accumulator becomes perceptibly shorter even
at full charge, you will need to replace it with a new one.
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MAN_Easyflex_com_eng_01.doc 49
4.3 Troubleshooting
The green indicator lamp does not light up after the unit has been
plugged into a mains outlet.
− Check the cable and connector for being firmly in position.
− Is the mains outlet live ?
The amber LED does not light up continuously although there is a
accumulator in the charger.
− Shortly disconnect the charger from the mains or on-board network.
− Has the accumulator been inserted properly (refer to Start-Up) ?
− Has the accumulator been pushed into the charger down to the stop ?
− Is the accumulator out of order ?
In case none of these hints allows you to solve the problem, please submit
the device to your service station for inspection or contact the Hagenuk
KMT hotline.
5 CARE UND MAINTENANCE
Neither the
Easyflex Com
nor any of its accessories contain components
which require regular care and maintenance to keep them operational.
Submit the
Easyflex Com
or its accessories to your service shop or to
Hagenuk KMT for repair should any defect occur.
Never use any aggressive solvent or detergent for cleaning your
Easyflex
Com
and its accessories. Use a soft, dry cloth for cleaning your
Easyflex
Com
and its accessories. When the device is very dirty, moisten the cloth
with some mild soap (do not use any abrasive agents) and clean it. Make
sure that all traces of moisture have evaporated before the
Easyflex Com
and its accessories are used again.
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6 APPENDIX
6.1 List of Abbreviations Used
ALT Alternating test
DC Direct current
EMV Electromagnetic compatibility
IEC International Electrotechnical Committee
LCD Liquid crystal display
LED Light emitting diode
NEXT Near end cross (X)-talk
NiMH Nickel metal hydrid
NVP Nominal velocity of propagation
TDR Time domain reflectometer
VDE Verein Deutscher Elektrotechniker
(Association of German Electrotechnical Engineers)
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MAN_Easyflex_com_eng_01.doc 51
6.2 Conversion: NVP ⇔⇔⇔⇔ v/2
Conversion NVP v/2 (m/µs)
2
s
m
299.79 • NVP
=
2
v
µ
Conversion v/2 ( m/µs) NVP
s
m
299.79
2
v
• 2
= NVP
µ
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52 MAN_Easyflex_com_eng_01.doc
6.3 Table: NVP and v/2 for Common Types of Cables
Typical propagation time
Insulation
v
/2 ,
m/µs
v
/2 , ft/µs
NVP
Oilimpregnated
paper
75-84 246-276
0.50-
0.56
Poly, crosslinked
78-87 256-285
0.52-
0.58
Poly, filled with
Petrolat
96.0 314.8 0.64
Polyethylene 100.5 329.6 0.67
PTFE 106.5 349.3 0.71
Paper 108-132 354-433
0.72-
0.88
Poly, foamed 122.9 403.4 0.82
Air 141-147 462-482
0.94-
0.98
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MAN_Easyflex_com_eng_01.doc 53
From your own measurements:
Propagation time
Insulation or
type of cable
v
/2, m/µs
v
/2, ft/µs
NVP
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54 MAN_Easyflex_com_eng_01.doc
6.4 Glossary
Resolution
In a → TDR device, resolution describes the minimum
distance between two successive faults in a cable at which
the events are depicted on the screen as individual echoes
which can be discriminated and, consequently, can be
measured. When the echoes superpose each other, the
starting time of the second echo – its so-called foot point –
cannot be measured. In this event the resolution is too
small. Resolution depends on the duration of the used
→ pulse. Obviously short pulses mean much better
resolution than long pulses. The distance range which can
be covered, on the other hand, is much shorter for short
pulses as compared with long ones.
Pulse
In a → TDR device, pulses are used as transmitter signals.
A pulse is an electrical signal with high amplitude and short
duration. When travelling along the cable, each pulse is
more and more deformed (attenuation of amplitude,
increase in signal duration). The width (duration) of a pulse
is measured between those points at which the pulse has
half its maximum amplitude. In locating a fault, its distance
is determined by moving the cursor to the foot point of the
echo – i.e. to its starting point. As each pulse grows wider
and wider when travelling along the cable, the achievable →
resolution is more and more reduced with growing distance.
(Factor of)
Propagation Time
NVP
Balancing Network
The balancing network is for simulating the input resistance
of the cable to be tested. It is used for suppressing the
display of the transmitter pulse so that reflections can be
depicted and measured directly from the output of the
Easyflex Com – there is no dead zone as otherwise usual.
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MAN_Easyflex_com_eng_01.doc 55
NEXT
Near End Cross (X) Talk
NEXT (Crosstalk) describes the coupling of signal
components into a neighbouring Pair running in parallel.
Crosstalk is undesirable as each component coupled into a
neighbouring pair will impair the signal-to-noise ratio in this
line. This is why in standards on data communication
equipment, certain minimum values are required for
crosstalk. Crosstalk attenuation is usually worst at the near
end, i.e. when one pair is used for transmission and another
pair for reception. Crosstalk may also be introduced by
other faults in the cable (e.g. a faulty junction box with
improper shielding of individual pairs from one another).
The Easyflex Com is able to locate these types of faults.
NVP
(= Nominal Velocity of Propagation)
The value of NVP, also called propagation time factor or
”reduction factor” (Verkuerzungsfaktor in German), is a way
to describe the propagation velocity of a signal along a line.
It specifies the ratio of signal propagation velocity to the
velocity of light. If, for instance, the NVP of a cable is
specified to be 0.65, the propagation velocity along the
cable is:
s
m
194.86 =
s
m
299.79 • 0.65 = c • NVP = v
µµ
where c = 299.79 m/µs velocity of light. There may be
differences between the information given in data leaflets or
the table in the manual and actual propagation times in real
objects due to the dependence of NVP on the material
used. As a rule, the difference is greater in balanced cables
than in coaxial cables. Moreover you have to reckon with
the individual pairs having slightly different values of NVP.
This has to be attributed to the fact that the shields of
different conductors contain different types of dye in order
to be able to distinguish individual conductors. As each dye
has a different value of ε
r
, signal propagation velocity is
different from pair to pair.
In the Easyflex Com, signal propagation velocity can be set
as either NVP or v/2.
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56 MAN_Easyflex_com_eng_01.doc
Impulse
→ Pulse
Split Pairs
Improperly connected, twisted two-wire connection.
The conductors of the individual pairs are not properly
twisted with each other in pairs. New pairs are generated by
the fact that at either end of the line one conductor is
reversed. Begin (split) and end (resplit) of the revered
section show strong crosstalk interference. Split Pairs are
the result of erroneous installation.
Pair
Pair of conductors of a balanced (symmetrical) line
STP
(= Shielded Twisted Pair)
Line which consists of a number of twisted two-wire pairs.
Each pair is wrapped in a foil shield of its own. By S/STP
(Screened Shielded Twisted Pair) a cable is understood the
entire body of which is enclosed in a common shield.
Balanced Line
Two-wire line with the voltages of either conductor versus
earth being equal in size but opposite in polarity. Usually
two-wire line are twisted (twisted pairs) to avoid any
interference effects.
TDR
(= Time Domain Reflectometer)
The Easyflex Com is a reflectometer operating in what is
known as the time domain. Apart from the amplitude, the
Easyflex Com measures exclusively propagation times with
the aim of calculating the distance to cable
inhomogeneities. In doing so it employs a different
operating principle than a frequency-domain instrument
(network channel analyser, spectrum analyser).
UTP
(= Unshielded Twisted Pair)
Line consisting of a number of twisted two-wire line pairs.
Unlike an STP cable, the individual pairs are not
shielded. By S/UTP (Screened Unshielded Twisted Pair) a
cable is understood the entire body of which is enclosed in
a common shield.
Page 57
MAN_Easyflex_com_eng_01.doc 57
v
/2
In cable testing it is common practice to specify the signal
propagation velocity in term of half the actual velocity.
When employing the reflection technique, this is a usual
way of taking twice the signal travel path into account. To
depict a reflection on the screen, the signal has to travel
from the meter to the fault and back. If the v/2 values of
various cables are listed in a table, these values can directly
be used to convert the measured signal propagation time tx
into fault distance E.
Reduction Factor
NVP (Nominal Velocity (of) propagation)
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