Sonel TDR-420 User manual

USER MANUAL
TDR CABLE FAULT LOCATOR
TDR-420
SONEL S.A.
Wokulskiego 11
58-100 Świdnica
Version 1.00 06.04.2018

TDR-420 – USER MANUAL2
TDR-420 is a modern, high-quality measuring device, easy and safe to use. Please acquaint yourself
with this manual in order to avoid measuring errors and prevent possible problems in operation of the
meter.

TDR-420 – USER MANUAL 3
CONTENTS
1 Introduction .................................................................................................4
2 Safety ...........................................................................................................4
3 Principle of operation .................................................................................5
4 Functional Description ...............................................................................6
5 Settings........................................................................................................8
5.1 Unit of the propagation factor..............................................................................8
5.2 Length units ........................................................................................................8
5.3 Screen brightness ...............................................................................................9
5.4 Auto-Off...............................................................................................................9
5.5 Language ..........................................................................................................10
6 Reflectometric measurements.................................................................11
6.1 Setting the parameters for fault location ...........................................................11
6.2 Value of wave impedance (Z) ...........................................................................12
6.3 Propagation factor VoP,....................................................................................12
6.3.1 Determining the unknown value of VoP ................................................................... 13
6.3.2 Measurement range - RANGE ................................................................................. 13
6.3.3 Operating modes of the reflectometer ...................................................................... 13
a. Mode of single fault location (ONCE) .................................................................... 14
b. Mode of continuous fault location (CONT) ............................................................ 14
c. Core identification mode (TONE) .......................................................................... 15
6.3.4 Selection of cursors (CUR) ...................................................................................... 15
6.3.5 GAIN........................................................................................................................ 16
6.3.6 Quick help................................................................................................................ 17
6.3.7 Measurement accuracy............................................................................................ 17
7 Connecting to the tested conductor .......................................................18
8 Power supply.............................................................................................19
8.1 Monitoring the power supply voltage.................................................................19
8.2 Replacing battery/rechargeable batteries .........................................................19
8.3 General principles regarding using Ni-MH rechargeable batteries ...................20
9 Cleaning and maintenance ......................................................................21
10 Storage.......................................................................................................21
11 Dismantling and Disposal ........................................................................21
12 Typical images of damaged cables.........................................................22
13 Typical values of VoP and impedance Z.................................................23
14 Technical data ...........................................................................................25
15 Accessories...............................................................................................26
16 Manufacturer .............................................................................................26
17 Laboratory services..................................................................................27

TDR-420 – USER MANUAL4
1 Introduction
TDR-420 is a handy Time-domain Reflectometer (TDR) designed to determine and locate faults
in:
•power cables,
•telecommunications cables,
•tele-technical cables.
The device allows user to measure the length of a cable and determine the distance of a fault
with the range of 7 to 6000 m in all almost types of metallic cables (e.g. copper or aluminium cables).
The shortest measuring range is 7 meters and a dead zone of 0.6 m.
TDR-420 displays the signals from the tested cable as a "trace" i.e. a waveform similar to an os-
cilloscope display. The trace is displayed on the LCD screen with a resolution of 320 x 240 pixels.
The distance to characteristic features - discontinuity points - may be read from the screen by placing
the cursor over these points. TDR-420 has the function of adjusting the output impedance to the
wave impedance of the tested cable, so that initial reflections at the beginning of the displayed trace
are reduced (reduction of the dead zone). This enables the user to locate damages within a short dis-
tance of the connected device.
The Velocity of Propagation factor (VoP) is adjusted within the range of 10%-99% (with respect to
the speed of light), i.e. V/2 = 15.0..148.5 m/μs, providing a precise adjustment of the propagation fac-
tor to the parameters of the tested cable. TDR-420 has also an internal signal generator to generate a
signal with sound frequency, which may be used to trace the cable route or identity cable pairs.
Due to continuous development of the meter’s software, the actual appearance of the
display, in case of some of the functions, may slightly differ from the display present-
ed in this user manual.
2 Safety
The following international symbols are used in the device and in this manual:
Warning;
See explanation in
the manual
Do not connect to sys-
tems with dangerous
voltage
Do not dispose of with
other household waste
Protection class II
(double or rein-
forced insulation)
Conformité
Européenne
In order to provide conditions for correct operation and the correctness of the obtained results,
the following recommendations must be observed:
•Before you proceed to operate the device, acquaint yourself thoroughly with this manual and ob-
serve the safety regulations and specifications defined by the producer.
•Any application that differs from those specified in the manual may result in a damage to the de-
vice and constitute a source of danger for the user.
•TDR-420 instruments must be operated only by appropriately qualified personnel with relevant
certificates authorising the personnel to perform works on electric systems. Unauthorized use of
the meter may result in its damage and may be a source of serious hazard to the user.
•Using this manual does not exclude the need to comply with occupational health and safety regu-
lations and with other relevant fire regulations required during the performance of a particular type
of work. Before starting the work with the device in special environments, e.g. potentially fire-
risk/explosive environment, it is necessary to consult it with the person responsible for health and
safety.

TDR-420 – USER MANUAL 5
•It is unacceptable to operate the device when:
a damaged meter which is completely or partially out of order,
a meter with damaged insulation,
a meter stored for an excessive period of time in disadvantageous conditions (e.g. excessive
humidity). If the meter has been transferred from a cool to a warm environment with a high level
of relative humidity, do not start measurements until the meter is warmed up to the ambient tem-
perature (approximately 30 minutes). Battery spill and damage to the meter may occur if dis-
charged batteries are left in the meter.
•Do not operate a meter with an open or incorrectly closed battery (accumulator) compartment or
power it from other sources than those specified in the present manual.
•Repairs may be performed only by an authorised service point.
CAUTION!
• Only standard and additional accessories for a given device should be used, as
listed in section 15 Accessories. Using other accessories may cause damage to
measuring terminals and introduce additional measurement uncertainty.
• Do not connect the device to cables under voltage. Under such conditions, the
measurement will be invalid, and the device may be damaged!
3 Principle of operation
TDR-420 measures time of signal run (probe pulse) through a cable pair from the connection
point (end of the dead zone) to the end of the cable or to the nearest damage. The reflectometer
may also determine the length of the section, where the cable insulation is wet, so the required
maintenance action may be taken.
The pulses transmitted by the device, run along the cable at the Velocity of Propagation (VoP),
which depends on the electrical parameters of the cable, particularly on the material of cable insula-
tion. Based on user-selected VoP value and the measured pulse time, the reflectometer:
•calculates the distance to the disturbance of wave impedance of the path and
•displays the image of the cable in the form of a reflectogram, which shows all discontinuities of
wave impedance in the tested section.
The horizontal axis is used to determine the length of the tested cable section as well as the dis-
tance to the damage and anomalies in the tested cable. The vertical axis is used to determine
changes in the impedance of the tested test cable.

TDR-420 – USER MANUAL6
4 Functional Description
To turn ON the device, briefly press . To turn OFF the device, press and hold button for
approx. 4 s.
After switching the device ON, the keypad backlight turns off automatically after approx. 20 s. If it
is not disabled with button, it turns on after pressing any other button.
After switching the device ON, it
displays the welcome screen
showing the software version ...

TDR-420 – USER MANUAL 7
... and then the main menu.
•Use buttons to select desired position.
•Press ENTER to proceed.
1. Measurements – here measurements are carried out after setting the following parameters:
wave impedance Z,
VoP - propagation factor,
measuring RANGE,
measurement mode,
the number of cursors,
gain.
The user may edit a selected parameter by pressing SET/SEL button – press it until the display
shows the desired item.
Selecting ? will display examples of the probe pulse shapes for different cable discontinuities
2. Settings – here user can set:
VoP unit,
length unit,
display brightness,
Auto-shutdown (idle time after which the device is turned off),
interface language.
Select the desired position using buttons and change settings with
buttons. The change is confirmed by pressing ENTER. Use ESC button to return to the
main menu without saving changes.
3. Help – here you can find a table with typical impedances and propagation velocities for different
types of cables.

TDR-420 – USER MANUAL8
5 Settings
5.1 Unit of the propagation factor
For exact location of the cable damage, set the correct velocity of propagation VoP of the probe
pulse. This is the basic parameter, related mainly to the type of insulation of the cable under test -
but also with the cable type and its age (VoP changes slightly due to the aging process). In addition,
remember that each individual cable manufacturer determines their propagation factor, which should
be presented in data sheets or other product documents.
At the end of this manual, examples of VoP are provided for basic cable types.
Velocity of Propagation (VoP) may be expressed in % of the speed of light or as V/2 – in feet or
meters per microsecond (µs). The selected unit becomes valid in measurements.
•Use buttons to select position 1. VoP unit.
•Use buttons to select VP% or m/μs(ft/μs).
•Confirm your choice by pressing ENTER. By pressing ESC button, you reject the changes.
5.2 Length units
•Use buttons to select position 2. Length unit.
•Use buttons to select meters or feet. Selection of the unit automatically switches
the unit of VoP (m/μs or ft/μs).
•Confirm your choice by pressing ENTER. By pressing ESC button, you reject the changes.

TDR-420 – USER MANUAL 9
5.3 Screen brightness
Selected screen brightness affects the operation time with one set of batteries.
•Use buttons to select position 3. Brightness.
•Use buttons to select one of the brightness levels: low, medium or high.
•Confirm your choice by pressing ENTER. By pressing ESC button, you reject the changes.
5.4 Auto-Off
TDR-420 has also Auto-off function. It reduces the energy consumed from the batteries, especial-
ly when the device is not switched OFF after the work.
•Use buttons to select position 4. Auto-Off.
•Use buttons to select the idle time, after which the device automatically switches OFF. Avail-
able settings: 1 - 3 - 5 - 10 - 15 min - Disable (function disabled).
•Confirm your choice by pressing ENTER. By pressing ESC button, you reject the changes.

TDR-420 – USER MANUAL10
5.5 Language
•Use buttons to select position 5. Language.
•Use buttons to select the one of the languages: Polish, Deutsch, Espanol, English.
•Confirm your choice by pressing ENTER. By pressing ESC button, you reject the changes.

TDR-420 – USER MANUAL 11
6 Reflectometric measurements
In the main menu, use buttons to select position 1. Measurements and press ENTER.
The screen shown below will be displayed.
Edit the selected parameter, by pressing shortly SET/SEL, until the display highlights the desired
item:
Setting the wave impedance Z
Setting the propagation factor VoP
Measurement range RANGE
Fault location mode:
CONT (continuous)
ONCE (single)
TONE (identification of cores with an acoustic signal)
Selection of the number of cursors CUR (note: this function is disabled in TONE mode)
Setting the sensitivity level GAIN (gain in the range from x1 to x8)
Useful help (reflectograms of typical waveforms of the reflected pulse for the most common
types of cable discontinuities)
Battery status indicator
Chart of the probe pulse
Indication of active cursor
Distance readout based on the cursor position
Distance readout between the discontinuities
6.1 Setting the parameters for fault location
From the measurement screen, user may set all the necessary parameters of the cable fault lo-
cation. Edit the selected parameter, by pressing shortly SET/SEL, until the display highlights the de-
sired item:
1. Value of wave impedance Z,
2. Propagation factor VoP,
3. Measurement RANGE,
4. Fault location mode,
5. Working with one or two cursors CUR,
6. Sensitivity level GAIN.
1 2 3 4
5
6
7
8
9
11
10
12
11

TDR-420 – USER MANUAL12
Change the setting value using buttons. The change is automatically saved in the device
memory.
The set parameters are stored in memory even after the device is turned off.
6.2 Value of wave impedance (Z)
Wave impedance Zis particularly important for certain types of cables, such as coaxial. In addi-
tion, proper selection of the impedance may be important for accurate fault location.
•Shortly press SET/SEL to select parameter Zfor editing.
•Use buttons to change the parameter value. Available settings: 25 - 50 - 75 - 100 - 120 Ω.
6.3 Propagation factor VoP,
•Shortly press SET/SEL to select parameter VoP for editing.
•Use buttons to change the parameter value. Range:
15.0…148.5 m/µs
50…495 ft/µs
10…99% Vc

TDR-420 – USER MANUAL 13
6.3.1 Determining the unknown value of VoP
If the value of the Velocity of Propagation VoP for the tested cable is not known, it can be deter-
mined as follows:
1. Use for the measurements a section of uniform cable with a length e.g. 10 m.
2. Measure the exact length of this cable using a centimetre rule or other method that ensures accu-
rate measurement.
3. Connect the reflectometer to the reference cable, set the cursor (sec. 6.3.4) at the beginning of
the pulse reflected from the cable end (evident break in the circuit) and adjust VoP value to ob-
tain the distance read-out identical with the physically measured length of cable. The value of
VoP determined in this way should be noted. It may be used for measurements on cables of the
same type.
• It is recommended that the reference section is as long as possible. Then, the cal-
culation error for VoP will be the lowest.
• Note that the VoP value selected in the above manner may be burdened with an er-
ror, and transfer error to further measurements on the same type of cable.
• Please note that the described method of calculating the VoP is considered as an
alternative. The surest solution is to use the value of the VoP defined by the manu-
facturer of cables.
6.3.2 Measurement range - RANGE
TDR-420 has 11 measuring ranges from 7 m to 6 km (20 ft …20 k ft).
•Shortly press SET/SEL to select parameter RANGE for editing.
•Use buttons to change the parameter value. Available values:
7 - 15 - 30 - 60 - 120 - 250 - 500 - 1 000 - 2 000 - 3 000 - 6 000 m
20 - 50 - 100 - 200 - 400 - 800 - 1 600 - 3 200 - 6 400 - 10 000 - 20 000 ft
6.3.3 Operating modes of the reflectometer
TDR-420 may operate in one of three modes:
ONCE - single,
CONT - continuous,
TONE - identification of cores with an acoustic signal.
•Shortly press SET/SEL to select the mode field.
•Use buttons to change the mode.

TDR-420 – USER MANUAL14
a. Mode of single fault location (ONCE)
After pressing START one probe pulse is sent. The user browses the reflectometric waveforms of
the cable, observing the scan result in different measuring ranges. The user places the cursor(s) in
the place of noticed cable damage to get an indication of the distance to this point (section 6.3.4).
b. Mode of continuous fault location (CONT)
After pressing START, the reflectometer sends and receives continuous probe pulses in the test-
ed pair of wires (cables), which enables it to identify of the instantaneous faults. The user observes
the waveforms of the cable, watching the results of the scanning in different measurement ranges
and places cursor(s) in the place of noticed cable damage to get an indication of the distance to this
point (section 6.3.4).

TDR-420 – USER MANUAL 15
c. Core identification mode (TONE)
TDR-420 may be also used as an acoustic signal generator for identifying pairs of cable and ca-
ble cores. For receiving this signal, inductive probes may be used, e.g. those used in telecommunica-
tions services, operating in the range of 810 ... 1110 Hz.
After selecting this mode, the reflectometer transmits a modulated audio signal via the cable
cores connected to test leads of the device for identification purposes.
In the mode of transmitting core identification signal, Auto-off function is disabled to
make the identification process last for the necessary period of time.
6.3.4 Selection of cursors (CUR)
In ONCE and CONT modes, the distance to the cable discontinuity is determined by using manu-
ally shifted cursors. The displayed distance translates proportionally to the distance from the end of
the dead zone to the point of placing the cursor.
To determine the distance to the discontinuity, place the cursor at the beginning of the pulse cor-
responding to this discontinuity. User may work:
with one cursor (red)
with two cursors (red and green).
•Shortly press SET/SEL to select parameter CUR.
•Use buttons to set the number of cursors.

TDR-420 – USER MANUAL16
Close to every cursor, the device displays the distance from the beginning of the cable. The bot-
tom of the measurement screen shows the difference in distance between two cursors.
The cursors are set by the user, so if they are set in the place of two discontinuities, then this will
be the distance between two discontinuities on the tested section - e.g. between branching and gap.
This allows user to obtain the length of the cable from the branching point
Cursor selection is made by pressing ENTER button. The active cursor is indicated by the arrow
in its upper part. It may be moved with buttons.
6.3.5 GAIN
This function is used to amplify the details of the waveform, especially in long cable sections.
For each of 11 measuring ranges, TDR-420 has a factory-set sensitivity level (amplification). In
addition, it is possible to manually adjust the gain (sensitivity) from 1-fold to 8-fold.
•Shortly press SET/SEL to select parameter GAIN.
•Use buttons to adjust the gain. Available values: x1, x2, x3, x4, x5, x6, x7, x8.

TDR-420 – USER MANUAL 17
6.3.6 Quick help
This function facilitates the interpretation of the obtained measurement result, when it is per-
formed. It enables the user to quickly determine the type of defect that occurs in the tested section of
the cable. The background of the reflectogram shows an auxiliary drawing, allowing observation and
comparison of the resulting waveform with typical waveform shapes.
•Shortly press SET/SEL to select the field marked with question mark ?.
•Use buttons to view the examples of pulse waveform, characteristic for typical defects
(discontinuities) of the cable.
6.3.7 Measurement accuracy
TDR-420 measures the distance to a cable damage and the length of cable with an accuracy of
+/- 1%. However, the actual measurement accuracy depends on the accuracy of determining
VoP for the tested cable, as well as on the stability of this factor over the entire length of the
cable. If the user set an incorrect value of VoP, or when this factor is not constant within the meas-
ured section, the measurement is burdened with an additional error.
• The value of VoP factor is lower for cables wound on a drum than for cables un-
wound and installed. Moreover, this factor may vary slightly for different types of ca-
bles and due to their ageing.
• The measurement accuracy of the distance to the damage depends on the correct
position the cursor on the waveform displayed by the reflectometer.

TDR-420 – USER MANUAL18
7 Connecting to the tested conductor
•Before connecting the device, make sure that the tested cable is disconnected from the power
source and receiving devices.
•The other end of the current path must be open or closed (not ended with resistance termination).
•Connect provided crocodile clips to the reflectometer (see figure).
•Connect the measurement terminals to one end of the cable under test.
Coaxial cable
Connect the red crocodile clip to the central wire of the cable and the black one to cable shield/braid.
Shielded cable
Connect the red crocodile clip to the wire nearest the shield and the black one to cable shield.
Twisted pair
The tested pair must be separated from the others. Connect the crocodile clips to the cores of the
tested pair.
Multi-conductor cable
The crocodile clips of the test leads should be connected to any two cable conductors/cores.