Megger MFT70-US User manual

MFT70-US
Multifunction Tester
With On - board memory
User Manual

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Contents
Contents
SAFETY WARNINGS 5
Live Ground safety precautions ........................................................................................................................6
Symbols used on the instrument are: ..............................................................................................................7
Introduction 8
Overview .........................................................................................................................................................8
Front panel and controls ..................................................................................................................................8
Display.............................................................................................................................................................8
Display symbols ..............................................................................................................................................9
Waste electrical and electronic equipment......................................................................................................10
Battery and fuse location, fitting and replacement .........................................................................................10
To replace batteries or fuse: ...........................................................................................................................10
For battery replacement:................................................................................................................................10
For fuse replacement .....................................................................................................................................10
Rechargeable batteries and battery charging..................................................................................................10
To charge the batteries:..................................................................................................................................11
Operation 12
General operation – all models.......................................................................................................................12
Switching on ...............................................................................................................................................12
Switching off ..............................................................................................................................................12
Backlight .....................................................................................................................................................12
Test buttons.................................................................................................................................................12
Test button lock ..........................................................................................................................................12
Mode button functions ............................................................................................................................13
Test inhibit .....................................................................................................................................................13
Insulation.......................................................................................................................................................13
Continuity ....................................................................................................................................................13
GFCI testing...................................................................................................................................................13
Ground testing ..............................................................................................................................................13
Battery exhausted ..........................................................................................................................................13
Voltage, frequency, current and temperature measurement............................................................................14
Making a voltage measurement.....................................................................................................................14
OR if using the mains plug lead SAI10:...........................................................................................................14
Frequency measurement ................................................................................................................................15
Phase rotation................................................................................................................................................15
Leakage current measurement ......................................................................................................................15
Temperature measurement ............................................................................................................................15
Switch probe .................................................................................................................................................15
Continuity / resistance measurement..............................................................................................................16
Nulling test lead resistance (up to 9.99 ohms) W.........................................................................................16

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Contents
To null test leads: ........................................................................................................................16
Making a continuity measurement.................................................................................................................17
Storing / downloading results.........................................................................................................................17
Continuity Buzzer ON/OFF..............................................................................................................................17
Switch probe (SP5).........................................................................................................................................18
Buzzer threshold............................................................................................................................................18
Measurement methods and sources of error ..................................................................................................18
Method of measurement .............................................................................................................................18
Possible sources of error...............................................................................................................................18
Insulation resistance 500
V.............................................................................18
Making an insulation measurement ...............................................................................................................19
Insulation test lock.......................................................................................................................................19
Measurement methods and sources of error ..................................................................................................20
Ground Fault Current Interrupt (GFCI) testing ................................................................................................20
Function button options ....................................................................................................................20
Ramp test ....................................................................................................................................................20
Making a measurement ...............................................................................................................................20
Touch voltage display...................................................................................................................................21
Measurement methods and sources of error ................................................................................................21
Useful information.......................................................................................................................................22
Ground resistance measurement....................................................................................................................22
Connection terminals...................................................................................................................................22
Touch voltage limit.......................................................................................................................................22
Making a measurement - two pole resistance measurement ........................................................................22
Making a measurement – three terminal resistance measurement ...............................................................23
Making a measurement – three terminal resistance measurement using ART ...............................................24
Two-clamp stake-less measurement .............................................................................................................25
Setup options 26
Warning messages.........................................................................................................................................27
Startup warnings ........................................................................................................................................27
Battery.........................................................................................................................................................27
Battery charger ............................................................................................................................................27
Fuse warning ...............................................................................................................................................27
Invalid rotary switch setting .........................................................................................................................27
Continuity test.............................................................................................................................................27
Insulation test ..............................................................................................................................................27
GFCI Test ....................................................................................................................................................27
GFCI range selection errors ..........................................................................................................................27
Test will not start ........................................................................................................................................28
Sending, Storing, Deleting and Recalling Test Results......................................................................................29

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Contents
Folders:........................................................................................................................................................29
Circuit type:.................................................................................................................................................29
Insulation:....................................................................................................................................................29
GFCI: ...........................................................................................................................................................30
Ground testing: ...........................................................................................................................................30
Storing Test Results in the internal memory ....................................................................................................30
Deleting Test Results from the internal memory............................................................................................30
Recalling Test Results to the display..............................................................................................................31
Sending stored test results via Bluetooth®....................................................................................................31
Sending individual (Blobbing) test results......................................................................................................31
Continuity testing ........................................................................................................................................32
GFCI testing.................................................................................................................................................32
Ground testing ...........................................................................................................................................32
Bluetooth®Pairing .........................................................................................................................................33
Bluetooth®Pairing (PC or Laptop) ................................................................................................................33
General Information 34
Installation category definitions....................................................................................................................34
Safe working practice ..................................................................................................................................34
Cleaning and maintenance ..........................................................................................................................34
Ground resistance testing – Basic principles....................................................................................................35
Principle of operation (three-terminal resistance measurement) ....................................................................35
Principle of operation (three-terminal resistance measurement using ART)....................................................35
Principle of operation (two-clamp stake-less resistance measurement)..........................................................36
General Specification .....................................................................................................................................37
Repair and Warranty ....................................................................................................................................39
CALIBRATION, REPAIR AND SPARE PARTS.....................................................................................................39
Deceleration of Conformity .............................................................................................................................

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SAFETY WARNINGS
SAFETY WARNINGS
Safety warnings and precautions must be read and understood before the instrument is used.
They must be observed during use.
Warnings:
• The circuit under test must be switched off, de-energised and isolated before test connections are
made when carrying out insulation and continuity tests.
• Continuity of protective conductors and Grounded equipotential bonding of new or modified
installations must be verified before carrying out an Ground fault loop impedance test, GFCI or
Ground testing
• Do not touch circuit connections and exposed metalwork of an installation or equipment under
test. Under fault conditions the system Ground could become hazardous live.
• Do not touch the Ground stakes, test leads and their terminations (including connections to
the Grounding system under test) if an installation Ground fault can arise, unless adequate
precautions are taken.
• The ‘live circuit warning’ and ‘automatic discharge’ functions are additional safety features and
should not be regarded as a substitute for normal safe working practices.
• Do not move the rotary switch positions while a test is in progress.
• Do not operate the instrument or connect it to any external system if it shows any visible signs
of damage or if it has been stored for prolonged periods in unfavourable conditions.
• Do not operate the instrument or connect it to any external system if the battery compartment
or casing is open or any parts of the case (including keypad, selector switch, display window,
etc.) are missing.
• Always disconnect the instrument from all systems while batteries are being changed or the fuse
replaced
• Do not replace rechargeable cells in the instrument with non-rechargeable “dry” cells and
attempt to charge the cells. This can cause explosion or fire.
• Do not operate charging equipment supplied with the instrument in damp or wet environments
or outdoors. All test leads must be removed from the instrument while charging.
• After insulation tests, capacitive circuits must be allowed to discharge before disconnecting
test leads. Locking the insulation test ON should only be used where there is no risk of a circuit
holding a charge.
• The instrument should not be used if any part of it is damaged.
• Test leads, probes and crocodile clips must be in good order, clean and with no broken or cracked
insulation.
• All test leads supplied with the instrument form part of the measuring circuit of the instrument.
They must not be modified or changed in any way, or be used with any other electrical
instrument or appliance.
• A plug severed from the power cord MUST be destroyed, as a plug with bare conductors is
hazardous in a live socket outlet.
• Ensure that hands remain behind guards of probes/clips when testing.
• U.K. Safety Authorities recommend the use of fused test leads when measuring voltage on high
energy systems.
• Replacement fuses must be of the correct type and rating.
• Failure to fit the correctly rated fuse will result in damage to the instrument in the event of an
overload.
• Special precautions are necessary when operating in situations where “live” Grounds may be
encountered: isolation switches and fuses (not supplied with this instrument) must be used.

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SAFETY WARNINGS
• Special precautions are necessary when working near high tension systems (MV and HV):
rubber gloves and shoes (not supplied with this instrument) should be worn.
• Special precautions are necessary when working in wet conditions or in agricultural
areas: observe the local safety standards and take all necessary special precautions applicable to
the particular location and do not touch the test leads with bare hands.
Live Ground safety precautions
A ‘Live’ ground is one that carries current from the mains supply, or could do so under fault conditions. The
following warnings apply in addition to those listed previously.
Warnings:
• All persons involved must be trained and competent in isolation and safety procedures for the
system to be worked on. They must be clearly instructed not to touch the Ground electrode,
test stakes, test leads, or their terminations if any ‘Live’ Grounds may be encountered. It is
recommended that they wear appropriate rubber gloves, rubber soled shoes, and stand on a
rubber mat.
• The Ground electrode under test should be isolated from the circuit it is protecting before testing
commences. If this is not possible, ART (attached Rod Technique) may be used to measure
electrode resistance.
• The instrument terminals should be connected to the system under test through isolation
switches that are rated to handle the likely maximum fault voltages and currents that could be
encountered at the installation. The isolation switch must be open whilst any personal contact
is made with the remote test stakes, or the connecting leads, e.g. when changing their position.
• The instrument terminals should be connected to the system under test through fuses that are
rated to handle the likely maximum fault voltages and currents that could be encountered at the
installation.
Note: This instrument must only be operated by suitably trained and competent people.
Users of this equipment and/or their employers are reminded that Health and Safety Legislation requires them to
carry out valid risk assessments of all electrical work so as to identify potential sources of electrical danger and risk
of electrical injury such as inadvertent short circuits. Where the assessments show that the risk is significant then
the use of fused test leads constructed in accordance with the HSE guidance not GS38 ‘Electrical Test Equipment
for use by Electricians’ should be used .
This instrument is internally protected against electrical damage when used for the purposes of testing low voltage
electrical installations as defined herein. If used in a manor other than those defined in this user guide, the
protection capabilities could be impaired with potential risk to the operator and the instrument.

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SAFETY WARNINGS
Symbols used on the instrument are:
GCaution: Refer to accompanying notes

Maximum 300 V a.c. CAT IV to Ground
> 600 V Maximum nominal system voltage of 600 V
fInstrument protected by 2 x F2 1000 V 30 kA fuses
cEquipment complies with current EU Directives
This equipment should be recycled as electronic waste
Equipment complies with ‘C tick’ requirements
12 V DC charger socket

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Introduction
Introduction
Congratulations on your purchase of a genuine Megger Multifunction tester. The MFT70 series Multi-function tester is a
compact instrument designed to perform all of the functions required by the electrical contractor to fully test domestic,
commercial and industrial wiring. Specially designed to comply with modern US International wiring regulations and
standards, the MFT70 may be used on all single and three phase systems with rated voltages up to 300 V AC rms to
ground.
Overview
Front panel and controls
Display
Test button
Lead Null
Test lock
Setup selector
Results store
Test lock
Setup selector
Touch voltage
contact point
Mode
Display
backlight
Display
Primary
functions
Secondary
functions
Test button
Lead Null

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Introduction
Display symbols
Symbol Meaning Symbol Meaning
lTest function locked on (also used to
indicate a change is saved in setup) GWarning triangle – instruction to refer to this user guide
zTest lead null active fFuse blown
UL= 50V Touch voltage limit (and Ground test
voltage) set to 50 V (change setup) Battery indicator
Buzzer enabled NiMH Battery type set to rechargeable NiMH -
Change in “Battery” on page 27
AUTO GFCI test in AUTO mode >100 V
Indicates that the ground noise voltage
exceeds the instrument measurement
capability (test is inhibited)
Type AC GFCI selected Rp (Rs)
Potential stake (P stake)
resistance exceeds range for accurate
measurement
Type A GFCI selected Rc (RH)
Current stake (C Stake)
resistance exceeds range for accurate
measurement
SType S GFCI (Type AC) V Ground noise voltage exceeds range for
accurate measurement of resistance
SType S GFCI (Type A) V Megger Voltage Clamp error
Type B GFCI selected I Megger Current Clamp error
Fast or Full RAMP test selected Bluetooth®enabled
TEST Instrument is running a test TInstrument is too hot, allow to cool
Ground loop noise detected.
N<->L Live and neutral connections reversed
Zref Reference loop measurement
R1+R2 Loop measurement with Zref value
automatically deducted
ZMAX Loop maximum measurement
NOTE: Some features detailed within this user guide are model dependent. Not all features appear on all models.

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Introduction
Waste electrical and electronic equipment
WEEE
The crossed out wheeled bin placed on Megger products is a reminder not to dispose of the product at the
end of its life with general waste. Follow local regulations.
Megger is registered in the UK as a producer of electrical and electronic equipment. The registration number
is WEE/HE0146QT
Battery and fuse location, fitting and replacement
Battery type: 6 x 1.5 V Alkaline LR6 (AA) or NiMH HR6 rechargeable
Fuse type: 2 x F2 1000 V 30 kA fuses
Battery condition is shown by the following display symbols:
Where NiMH rechargeable batteries are fitted, the battery condition display can be adjusted accordingly. Refer to
“Setup options” on page 26 to change between alkaline and rechargeable batteries.
When set to NiMH batteries, the battery indicator in the display will show NiMH under the battery status symbol
as below: (Feature available on all models).
To replace batteries or fuse:
Switch off the instrument.
Disconnect the instrument from any electrical circuits.
Remove the battery cover from the base.
For battery replacement:
Remove old cells and refit new batteries following correct polarity as marked on the battery holder.
Replace the battery cover.
Incorrect battery cell polarity can cause electrolyte leakage, resulting in damage to the instrument.
For fuse replacement
Withdraw each fuse in turn and check for failure. The blown fuse must be replaced with a F2 1000 V 30 kA fuse.
Rechargeable batteries and battery charging
Some models are supplied with rechargeable NiMH cells. These batteries can be charged in the instrument, using
the supplied Megger charger.
NiMH