Kewtech KT62 User manual

KEWTECH
KT62 digital multi function tester
Instruction manual

Contents 1 Safe testing 1
2 Features 3
3 Specification 6
4 Continuity (resistance) tests 9
4.1 Instrument layout 9
4.2 Test procedure 9
5 Insulation tests 11
5.1 The nature of insulation resistance 11
5.1.2 Capacitive current 11
5.1.3 Conduction current 12
5.1.4 Surface leakage current 12
5.1.5 Total leakage current 13
5.2 Damage to voltage sensitive equipment 13
5.3 Preparation for measurement 14
5.4 Insulation resistance measurement 14
6 Loop Impedance tests 17
6.1 Voltage measurement 17
6.2 What is earth fault loop impedance? 17
6.3 Automatic over temperature cut out 17
6.4 The loop impedance test 17
6.5 Loop impedance at 3 phase equipment 19
7 Prospective Short Circuit Current (PSC) tests 21
7.1 What is Prospective Short Circuit? 21
7 2 Testing Prospective Short Circuit Current 21
8 RCD tests 23
8.1 Purpose of RCD Test 23
8.2 What does the RCD test really do 23
8.3 RCD testing 23
8.4 Testing RCD's used to provide supplementary protection 24
8.5 Testing time delayed RCD's 25
8.6 Testing DC sensitive RCD's 25
9 General 26
10 Battery replacement 26
11 Fuse replacement 26
12 Servicing 27
13 Case and strap assembly 27

1 Safe Testing
1
Electricity is dangerous and can cause injury and death. Always
treat it with the greatest of respect and care. If you are not quite
sure how to proceed, stop and take advice from a qualified person.
1 This instrument must only be used by a competent and trained person
and operated in strict accordance with the instructions. Kewtech will
not accept liability for any damage or injury caused by misuse or non-
compliance with the instructions or with the safety procedures.
2 It is essential to read and to understand the safety rules contained in
the instructions. They must always be observed when using the
instrument.
3 This instrument is intended only for single phase operation at 230V AC
+10%-15% phase to earth or phase to neutral operation, and then
only for loop, prospective short circuit current (PSC) and RCD testing.
For use in the continuity testing and insulation testing modes this
instrument must be used ONLY on circuits which are de-
energised.
4 When conducting tests do not touch any exposed metalwork
associated with the installation. Such metalwork may become live for
the duration of the test.
5 Never open the instrument case (except for fuse and battery
replacement and in this case disconnect all leads first) because
dangerous voltages are present. Only fully trained and competent
electrical engineers should open the case. If a fault develops, return the
instrument to Kewtech for inspection and repair.
6 If the overheat symbol appears in the display disconnect the
instrument from the mains supply and allow to cool down.
7 For loop impedance tests to prevent unwanted tripping during loop
testing all residual current devices (RCDs) must be taken out of the
circuit and temporarily replaced with a suitably rated MCB unit. The
RCD must be replaced after the loop test is completed.
8 If abnormal conditions of any sort are noted (such as a faulty display,
unexpected readings, broken case, cracked test leads, etc) do not use
the tester and return it to Kewtech for repair.
9 For safety reasons only use accessories (test leads, probes, fuses,
cases, etc) designed to be used with this instrument and
recommended by Kewtech. The use of other accessories is prohibited
as they are unlikely to have the correct safety features.
10 When testing, always be sure to keep your fingers behind the safety
barriers on the test leads.

Safe testing
2
11 During testing it is possible that there may be a momentary
degradation of the reading due to the presence of excessive transients
or discharges on the electrical system under test. Should this be
observed, the test must be repeated to obtain a correct reading. If in
doubt, contact Kewtech.
12 The sliding shutter on the back of the instrument is a safety device. The
instrument should not be used if it is damaged or impaired in any way,
but returned to Kewtech for attention.
13 Kewtech recommends the use of fused test leads particularly when
measuring voltages in high energy circuits. Where assessments show
that the risk is significant, then the use of fuse test leads constructed in
accordance with the HSE Guidance Note GS38 should be used. The
test accessories used with this instrument for loop impedance and
RCD tests are all fused.
14 Do not operate the function selector whilst the instrument is
connected to a circuit. If, for example, the instrument has just
completed a continuity test and an insulation test is to follow,
disconnect the test leads from the circuit before moving the selector
switch.
15 Do not rotate function dial when test button is depressed. If the
function switch is inadvertently moved to a new function when the test
button is depressed or in lock-down position the test in progress will
be halted.
16 Always check the test lead resistance before carrying out tests. This
ensures the leads are ok before taking measurements. The resistance
of leads and/or crocodile clips may be significant when measuring low
resistances. If crocodile clips can be avoided for low resistance
measurements , this will reduce the error due to lead accessories
17 When carrying out Insulation Resistance tests, always release the test
button and wait for charged capacitances to totally discharge before
removing the test leads from the test circuit.
BATTERY LIFE
Always switch the selector dial to the OFF position after each testing
period. This will conserve battery power.
INSULATION/CONTINUITY TESTS
Only use the test leads supplied with this tester and always ensure that
they are plugged fully into the unit’s 4mm terminals to guarantee a
sound and proper connection.

2 Features
3
Connector
Live circuit LED
Phase switch
Polarity switch
Continuity null switch
RCD rated tripping
current switch
Function switch
Wiring check LED
LCD display
Test button
LCD display
Test Lead with IEC Connector
Test Lead for Continuity
and Insulation Testing
Fig. 1

Features
4
The KT62 Multi-Function tester performs six functions in one instrument.
1 Continuity tester
2 Insulation resistance tester
3 Loop impedance tester
4 Prospective short circuit current tester
5 RCD tester
6 Mains voltage warning when operating the loop impedance and
RCD mode.
The tester is designed to Safety Standard IEC 1010-1/BS EN 61010-1
CAT III(300V).
The instrument is supplied with:
1Adistribution board or lighting circuit test lead for
LOOP/PSC/RCD testing.
2 A lead for LOOP/RCD testing at socket outlets.
3 A lead for insulation and continuity testing.
4 External Earth Probe for loop testing.
In the insulation resistance testing mode the instrument provides a rated
current of1mA as required in BS 7671 (IEE Wiring Regulations) and BS EN
61557-2 1997.
In the continuity testing mode the instrument provides a short circuit
current of 200mA as required in BS 7671 (IEE Wiring Regulations) and BS
EN 61557-4 1997.
Continuity and insulation resistance functions have the following features:
Live circuit warning A colour coded LED warns if the circuit
under test is live.
Continuity Null Allows automatic subtraction of test
lead resistance from continuity
measurements.
Polarity switch Allows switching of polarity during
continuity tests.
Auto discharge Electric charges stored in capacitive circuits
are discharged automatically after testing
by releasing the test button.

Features
5
Loop impedance, PSC and RCD testing functions have the following
features:
Voltage level In the LOOP/PSC/RCD modes, supply
voltage is displayed when the instrument is
connected to the supply until the test button
is pressed.
Wiring check Three LEDs indicate if the wiring of the
circuit under test is correct.
Over temperature Detects overheating of the internal
protection resistor (used for LOOP and PSC tests) and of
the current control MOS FET (used for RCD
tests) displaying a warning symbol and
automatically halting further measurements.
Phase angle selector The test can be selected from either the
positive (0˚) or from the negative (180˚) half-
cycle of voltage. This selector is used in the
RCD mode to obtain the maximum trip time
of an RCD for the test selected.
DC Test Allows testing of RCDs which are sensitive to
DC fault currents.
Auto data hold Holds the displayed reading for a time after
the test is complete.
Auto power off Automatically switches the instrument off
after a period of approximately 10 minutes.
The Auto power off made can only be
cancelled when the Function switch is
switched to the OFF position and then back
on.
V-NE Monitoring Automatically aborts measurement when the
Circuit N-E voltage rises to 50V or greater on RCD
ranges.

Specification
6
Measurement Specification
Function Open Circuit
Voltage (DC)
Short Circuit
Current Range Accuracy
Function Open Circuit
Voltage (DC)
Rated
Current Range Accuracy
Function Rated
Voltage (AC)
Nominal Test
Current at 0Ω
External Loop
Range Accuracy
Continuity Greater than
6V
Greater than
200mA as per
BS7671
20/200/2000Ω
Auto-Ranging
±(1.5%rdg
+3dgt)
250V+40%
-0%
1mA or greater
@ 250kΩas per
BS7671
20/200MΩ
Auto-Ranging
±(1.5%rdg
+3dgt)
500V+30%
-0%
1mA or greater
@ 500kΩas per
BS7671
20/200MΩ
Auto-Ranging
±(1.5%rdg
+3dgt)
1000V+20%
-0%
1mA or greater
@ 1MΩas per
BS7671
20/200MΩ
Auto-Ranging
±(1.5%rdg
+3dgt)
Insulation
Resistance
230V+10% -15% 50Hz
230V+10% -15% 50Hz
230V+10% -15% 50Hz
Loop
Impedance
25A
15mA
15mA
±(3%rdg+4dgt)
±(3%rdg+8dgt)
±(3%rdg+4dgt)
20Ω
200Ω
2000Ω
230V+10%
-15% 50Hz
Prospective
Short Circuit
Current
(PSC)
15mA
25A
25A
PSC accuracy is
derived from
measured loop
impedance
specification
and measured
voltage
specification
200A
2000A
20kA

Specification
7
Function Rated
Voltage (AC)
Trip Current
Trip Current
Duration
Accuracy
Function Rated voltage Measuring
Range Accuracy
Voltage measurement- 100-250V 100-250V 3% rdg
RCD
x 1/2
230V+10%
-15% 50Hz
230V+10%
-15% 50Hz
Trip Current:
-10% +0% of
range at 230V
Trip Current:
+10% -0% of
range at 230V
Trip Current:
+10% -0% of
range at 230V
RCD
x 1
10/30/100/300/
500/1000 mA
10/30/100/300/
500/1000 mA
2000ms
2000ms
1000mA
@200ms
Trip Current:
±10% of
range at 230V
RCD
x 5
230V+10%
- 15% 50Hz
10 mA
30/100/300mA
(Note: on x5 range
max. current that can
be generated is 1A)
50ms
Trip
Time±
(1% rdg
+3dgt)
To prevent wrong connection of test leads and to maintain safety, the
dedicated terminals used for continuity and insulation tests are
automatically covered when using the terminals for loop impedance, PSC
and RCD tests.
Instrument dimensions130 X 183 X 100mm
Instrument weight 1130g including batteries.
Reference conditions Specifications are based on the following
conditions except where otherwise stated:-
1Ambient temperature: 23±2˚C
2Relative humidity 45% to 75%
3Position: horizontal
4AC power source 230V, 50Hz
5DC power source: 12.0 V, ripple content
1% or less
6Altitude up to 2000m

Specification
8
Battery type Eight AA ALKALINE batteries.
Low battery warning symbol appears in the display and the
buzzer beeps if the battery voltage drops
below 7.8V.
Operating temperature 0 to +40˚C, relative humidity 80% or less, no
and humidity. condensation.
Storage temperature -10 to +50˚C, relative humidity 75% or less,
and humidity no condensation.
LED indication of live Illuminates if there is an alternating voltage of
circuit warning 50V AC or more in the circuit under test
before continuity or insulation resistance tests.
When DC voltage is detected across the
measuring terminal the LED lights up.
LED indication of The P-E and P-N LEDs illuminate when the
correct polarity wiring of the circuit under test is correct.
The reverse lamp is lit when P and N are
reversed.
Auto data hold In the loop impedance, PSC and RCD test
functions, the LCD reading is automatically
frozen for 3 seconds after measurement.
Display The liquid crystal display has 3 1/2 digits with a
decimal point and units of measurement (Ω,
MΩ, A, kA,V and ms) relative to selected
function. The display is updated approximately
five times per second.
Overload protection The continuity test circuit is protected by a
0.5A 600V fast acting (HRC) ceramic fuse
mounted in the battery compartment, where a
spare fuse is also stored.
The insulation resistance test circuit is
protected by a resistor against 1000 V AC for
10 seconds.
Mains Voltage On connecting test leads to the circuit under
Indication test on LOOP, PSC and RCD ranges, the LCD
reads V-PE. Sign ‘V-PE Lo’ or ‘V-PE Hi’ is also
shown when the voltage is 100V or less, or
260V or greater respectively.
+_
LO

4 Continuity
(resistance) tests
9
Warning: Ensure that circuits to be tested are not live.
Disconnect the instrument from the circuit under test before
operating the function switch.
To select the low resistance range select ‘CONTINUITY’.
4.1 Instrument layout - see Fig 1 on page 3.
4.2 Test Procedure
The object of continuity testing is to measure only the resistance of the
parts of the wiring system under test. This measurement should not
include the resistance of any test leads used. The resistance of the test
leads needs to be subtracted from any continuity measurement. The KT62
is provided with a continuity null feature which allows automatic
compensation for any test lead resistance.
You should only use the test leads supplied with the instrument.
Proceed as follows:-
1Select the continuity test by rotating the function dial.
2Connect the ends of the test leads firmly together (see Fig 2) and press
and lock down the test button. The value of the lead resistance will be
displayed.
3Operate the Continuity Null button, this will null out the lead
resistance and the indicated reading should go to zero.
4Release the test button. Press the test button and ensure the display
reads zero before proceeding. While using the Continuity null function,
the Ωsymbol will flash. The null value will be stored even if the
function switch is turned to the OFF position. This memorized null
value can be cancelled by disconnecting the test leads and pushing the
Continuity Null button with the test button pressed or locked. When
Fig. 2

Continuity
(resistance) tests
10
this is cancelled you will know because the Ωsymbol will not flash.
CAUTION - before taking any measurements always check the leads
have been zeroed.
5Connect the test leads to the circuit whose resistance is required (see
Fig 3 for a typical connection arrangement), having first made sure
that the circuit is not live. Note that the live circuit warning lamp
will illuminate if the circuit is live - but check first anyway!
6Press the test button and read the circuit resistance from the display.
The reading will have the test lead resistance already subtracted if the
Continuity null function has been used.
7Note that if the circuit resistance is greater than 20Ωthe instrument
will autorange to the 200Ω, if it is greater than 200Ωit will autorange
to the 2000Ωrange.
Note: If the reading is greater than 2000Ωthe overange symbol
‘OL’ will remain displayed.
The KT62 is provided with a facility to change the polarity of the test
current used by the instrument during continuity tests. To use this function
proceed as follows:-
1Perform a continuity test as outlined in the procedures above.
2Operate the polarity switch if required.
3Repeat the continuity tests and the polarity of the test current will be
reversed.
Temporary link Test at socket
between L and E
Fig 3

5 Insulation tests
11
Warning: Ensure that circuits to be tested are not live.
Disconnect the instrument from the circuit under test before
operating the function switch.
To select the insulation resistance range select ‘INSULATION’.
5.1 The nature of insulation resistance
Live conductors are separated from each other and from earth metal by
insulation, which has a resistance which is high enough to ensure that the
current between conductors and to earth is kept at an acceptably low
level. Ideally insulation resistance is infinite and no current should be able
to flow through it. In practice, there will normally be a current between
live conductors and to earth, and this is known as leakage current. This
current is made up of three components, which are:-
1. capacitive current
2. conduction current, and
3. surface leakage current.
5.1.2 Capacitive Current
The insulation between conductors which have a potential difference
between them behaves as the dielectric of a capacitor, the conductors
acting as the capacitor plates. When a direct voltage is applied to the
conductors, a charging current will flow to the system which will die away
to zero (usually in less than a second) when the effective capacitor
becomes charged. This charge must be removed from the system at the
end of the test, a function which is automatically performed by the KT62.
If an alternating voltage is applied between the conductors, the system
continuously charges and discharges as the applied voltage alternates, so
that there is a continuous alternating leakage current flowing to the
system.

Insulation tests
12
Insulation (acting as dielectric)
Insulation (acting as resistance)
Conductor (acting
as capacitor plates)
Conductors
Capacitive effect
Insulation
Conductors
Surface leakage current
Fig 4
5.1.3 Conduction Current
Since the insulation resistance is not infinite, a small leakage current flows
through the insulation between conductors. Since Ohm's Law applies, the
leakage current can be calculated from
Leakage current (µA) = applied voltage (V)
insulation resistance (MΩ)
Fig 5
5.1.4 Surface Leakage Current
Where insulation is removed, for the connection of conductors and so on,
current will flow across the surfaces of the insulation between the bare
conductors. The amount of leakage current depends on the condition of
the surfaces of the insulation between the conductors. If the surfaces are
clean and dry, the value of the leakage current will be very small. Where
the surfaces are wet and/or dirty, the surface leakage current may be
significant. If it becomes large enough, it may constitute a flashover
between the conductors.
Whether this happens depends on the condition of the insulation surfaces
and on the applied voltage; this is why insulation tests are carried out at
higher voltages than those normally applying to the circuit concerned.
Fig 6
Resistance effect

Insulation tests
13
5.1.5 Total Leakage Current
The total leakage current is the sum of the capacitive, conduction and
surface leakage current described above. Each of the currents, and hence
the total leakage current, is affected by factors such as ambient
temperature, conductor temperature, humidity and the applied voltage.
If the circuit has alternating voltage applied, the capacitive current (5.1.2)
will always be present and can never be eliminated. This is why a direct
voltage is used for insulation resistance measurement, the leakage current
in this case quickly falling to zero so that it has no effect on the
measurement. A high voltage is used because this will often break down
poor insulation and cause flashover due to surface leakage (see 5.1.4), thus
showing up potential faults which would not be present at lower levels.
The insulation tester measures the applied voltage level and the leakage
current through the insulation. These values are internally calculated to
give the insulation resistance using the expression:-
Insulation resistance (MΩ) = Test voltage (V)
Leakage current (µA
As the capacitance of the system charges up, so the charging current falls
to zero and a steady insulation resistance reading indicates that the
capacitance of the system is fully charged. The system is charged to the full
test voltage, and will be dangerous if left with this charge. The KT62
provides an automatic path for discharging current as soon as the test
button is released to ensure that the circuit under test is safely discharged.
If the wiring system is wet and/or dirty, the surface leakage component of
the leakage current will be high, resulting in low insulation resistance
reading. In the case of a very large electrical installation, all the individual
circuit insulation resistances are effectively in parallel and the overall
resistance reading will be low. The greater the number of circuits
connected in parallel the lower will be the overall insulation resistance.
5.2 Damage to Voltage-Sensitive Equipment
An increasing number of electronic-based items of equipment are being
connected to electrical installations. The solid state circuits in such
equipment are likely to be damaged by the application of the levels of
voltage used to test insulation resistance. To prevent such damage, it is
important that voltage-sensitive equipment is disconnected from the
installation before the test is carried out and reconnected again
immediately afterwards. The devices which may need to be disconnected

Insulation tests
14
before the test include:-
▲Electronic fluorescent starter switches
▲Passive infra-red detectors (PIRs)
▲Dimmer switches
▲Touch switches
▲Delay timers
▲Power controllers
▲Emergency lighting units
▲Electronic RCDs
▲Computers and printers
▲Electronic point-of-sale terminals (cash registers)
▲Any other device which includes electronic components.
5.3 Preparation for measurement
Before testing, always check the following:-
1The ‘low battery’ Indication is not displayed
2 There is no visually obvious damage to the tester or to the test
leads
3 Test the continuity of the test leads by switching to continuity test
and shorting out the lead ends. A high reading will indicate that
there is a faulty lead or that the fuse is blown.
4 Make sure the circuit to be tested is not live. A warning
lamp is lit if the instrument is connected to a live circuit but test
the circuit as well!
5.4 Insulation resistance measurement
The KT62 has a selectable, triple test voltage of 250V, 500V and 1000V
DC.
1Select the insulation resistance setting by rotating the function
dial to the required test voltage - 250V, 500V or 1000V as
indicated under the ‘insulation’ test section of the functional
switch, after making sure that the instrument is not connected to
a live circuit.
2 Attach the test leads to the instrument and to the circuit or the
appliance under test (see Figs 7 & 8)
+_
LO

Insulation tests
15
All fuses in or circuit
breakers closed
Mains switch open
Equipment disconnected
Switches closed Lamps out
Reading not less
than 0.5 MΩ
Main
switch
open
Note: insulation testing must only be undertaken on
de-energised circuits
Fig 7
3If the mains warning lamp lights and/or the buzzer sounds do not
press the test button but disconnect the instrument from the circuit.
Make the circuit dead before proceeding.
Fig 8
4Press the test button when the display will show the insulation
resistance of the circuit or the appliance to which the instrument is
connected.
5Note that if the circuit resistance is greater than 20MΩthe instrument
will automatically range to the 200MΩreading.

Insulation tests
16
6When testing is complete release the test button before disconnecting
the test leads from the circuit or from the appliance. This will ensure
that the charge built up by the circuit or the appliance during insulation
test is dissipated in the discharge circuit. In the discharging process, an
LED illuminates and the live circuit warning buzzer will sound.
CAUTION
Never turn the function dial whilst the test button is depressed as
this may damage the instrument. Never touch the circuit, test lead
tips or the appliance under test during insulation testing.
Always release the test button first after testing before removing
the test leads from the circuit. This is to ensure that charges
stored in the circuit capacitance have been totally discharged.
Note: If the reading measured greater than 200MΩthe over range
reading ‘OL’ will be displayed.

6 Loop impedance
tests
17
Disconnect the instrument from the circuit under test before
operating the function switch.
To select the loop testing range select ‘LOOP’.
6.1 Voltage Measurement
When the tester is set to the loop test function, mains voltage is displayed
as soon as the instrument is connected for test. This voltage display is
automatically updated five times every seconds. The voltage function
operates whenever the test button is in the up position.
6.2 What is earth fault loop impedance?
The path followed by fault current as a result of a low impedance fault
occurring between the phase conductor and earth is called earth fault
loop. Fault current is driven round the loop by the supply voltage, the
amount of current depending on the voltage of the supply and on the
impedance of the loop. The higher the impedance, the lower will be the
fault current and the longer it will take for the circuit protection (fuse or
circuit breaker) to operate and interrupt the fault.
To make sure that fuses will blow or that circuit breakers will operate
quickly enough in the event of a fault, the loop impedance must be low, the
actual maximum value depending on the characteristics of the fuse or the
circuit breaker concerned. The IEE Regulations (BS 7671) provides tables
showing the maximum permissible values of loop impedance in circuits
protected by various fuses and circuit breakers. Every circuit must be
tested to make sure that the actual loop impedance does not exceed that
specified for the protective device concerned.
6.3 Automatic over-temperature cut-out
During the short test period the instrument operates at high power. If
frequent tests are conducted over a prolonged period of time, the internal
test resistor will overheat. When this happens, further tests are
automatically inhibited and the over-temperature symbol appears in the
display. The instrument must then be left to cool down, after which testing
may be resumed.
6.4 The loop impedance test
Since the earth fault loop is made up of conducting path which includes the
supply system back to the supply transformer, it follows that loop testing
can only be carried out after the mains supply has been connected. In
many cases, any RCD in the circuit will be tripped by this test, which draws
current from the phase and returns it through the earth system. The RCD

Loop impedance
tests
18
will see this as the type of fault it is designed to protect against, and will
trip. To prevent this unwanted RCD tripping during loop testing, any RCD
must be taken out of circuit and temporarily replaced with a suitably rated
MCB unit. The RCD will need to be replaced after the loop test is
completed.
WARNING
Do not proceed with testing unless the P-E and P-N lamps are lit
to confirm that the wiring is correctly connected. Should these two
lamps not be lit, investigate the wiring connections of the
installation and rectify any faults before proceeding with the test.
If the red LED is lit do not proceed.
1Set the instrument to loop test 20Ωrange.
2If testing sockets, connect the plug lead to the KT62 and push the
moulded plug into the socket to be tested (see Fig 9).
3Check that the wiring lamps are lit Green (PE), Green (PN) and the
third red LED is OFF
4Note the mains voltage displayed by the instrument.
5Press the ‘Press to test’ button. The value of the measured loop
impedance will be displayed with the appropriate units. The test will
start at the sound of a bleep. Whilst the test is being conducted the
display will show a series of moving square symbols (see below). When
these stop the measurement value will be displayed.
6If testing lighting or other circuits, connect the three-wire lead to the
KT62, connect the red (phase) lead to the phase connection of the
circuit under test, connect the black (neutral) lead to the neutral
connection of the circuit under test, and connect the earth lead to the
earth associated with the circuit. (see Fig 10).
7The measuring ranges 200Ωand 2000Ωuse a low test current.
Therefore it will be possible to carry out a loop impedance test in the
presence of RCD's rated at 30mA or above (assuming that there is no
other earth leakage on the circuit being tested). Note that readings
below 15Ωwill be subject to significant variances due to the fact that