Major tech MT550 User manual

INSTRUCTION MANUAL
DIGITAL
INSULATION TESTER
MT550

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Contents Page no
1. Safety Information.............................................................................4
2. Safety Symbols..................................................................................4
3. Specifications....................................................................................4
3.1. General Information.................................................................4
3.2. Electrical Specifications............................................................5
4. Parts & Controls.................................................................................7
5. Battery Replacement.........................................................................7
5.1. How to connect test leads.........................................................7
5.2. Battery Check-UP & Replacement...............................................7
5.3. Test Lead Check.......................................................................7
6. Insulation Resistance Measurements...................................................8
6.1. Measurements at 200MΩ/250V..................................................8
6.2. Measurements at 2000MΩ/1000V..............................................8
6.3. Lock Power On Feature.............................................................8
7. Low Resistance (Continuity) Measurements..........................................9
8. AC/DC Voltage Measurements............................................................9
9. Power Tools and Small Appliances........................................................9

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1. SAFETY INFORMATION
• Read the following safety information carefully before attempting to
operate or service the meter.
• To avoid damages to the instrument do not apply the signals which
exceed the maximum limits shown in the technical specifications tables.
• Do not use the meter or test leads if they look damaged. Use extreme
caution when working around bare conductors or bus bars.
• Accidental contact with the conductor could result in electric shock.
• Use the meter only as specified in this manual; otherwise, the protection
provided by the meter may be impaired.
• Read the operating instructions before use and follow all safety
Information.
• Caution when working with voltages above 60V DC or 30V AC RMS. Such
voltages pose a shock hazard.
• Before taking resistance measurements or testing acoustic continuity,
disconnect circuit from main power supply and all loads from the circuit.
2. SAFETY SYMBOLS
Caution refer to this manual before using the meter.
Dangerous voltages.
Meter is protected throughout by double insulation or reinforced
insulation.
When servicing, use only specified replacement parts.
CE Comply with EN-61010-1
3. SPECIFICATIONS
3.1. General Information
Environment conditions:
1. Installation Categories III
2. Pollution Degree 2
3. Altitude up to 2000 meters
4. Indoor use only
5. Relatively humidity 80% max.
6. Operation Ambient 0~40ºC
Maintenance & Cleaning:
1. Repairs or servicing not covered in this manual should only be
performed by qualified personnel.
2. Periodically wipe the case with a dry cloth. Do not use abrasives or
solvents on this instruments.

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Accuracies are specified in the way:
±(…% of reading +…digits) at 23ºC±5ºC, below 80% RH.
Display Large LCD with dual display
Measurement Range 200Ω, 200kΩ, 200MΩ/250V, 200MΩ/500V,
2000MΩ/1000V, 750V/ACV, 1000V/DCV.
Sampling Rate 2.5 times per second.
Zero Adjustment Automatic adjustment.
Over Range Indicator Number 1 of highest digit is displayed.
Low Battery Indication The is displayed when the battery Voltage
drops below the operating voltage.
Operating Temperature 0ºC to 40ºC (32ºF to 104ºF) and Humidity
below 80% RH
Storage Temperature -10ºC to 60ºC (14ºF to 140ºF) and Humidity
below 70% RH
Battery 6 x AA
Dimensions 200(L) x 92(W) x 50(H) mm
Weight Approx. 700g include battery
Accessories Test Leads, 6 Batteries, Carrying Case, Manual.
Function Range
3.2. Electrical Specifications
OHMS
Range Resolution Accuracy Max. open Overload
Circuit Protection
Voltage
200Ω 0.01Ω 4.5V
±(1%+2) 250Vrms
200kΩ 0.1Ω 3.0V
Continuity Beeper
Range Resolution Accuracy Max. open Overload
Circuit Protection
Voltage
0.1Ω Resistance≤40Ω 4.5V 250Vrms
Short circuit current ≤200mA

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DC Voltage
Range Resolution Accuracy Input Overload
Impedance Protection
1000V 1V ±(0.8%+3) 10MΩ 1000Vrms
AC Voltage (40Hz~400Hz)
Range Resolution Accuracy Input Overload
Impedance Protection
750V 1V ±(1.2%+10) 10MΩ 750Vrms
Meg OHMS
Range Resolution Accuracy Terminal Voltage
200MΩ/250V 0.1MΩ 250V +10%~-0%
±(3%+5)
200MΩ/500V 0.1MΩ 500V +10%~-0%
0~1000MΩ/1000V
1000~2000MΩ 1MΩ ±(5%+5) 1000V +10%~-0%
/1000V
Range Test Current Short Circuit Current
200MΩ/250V 250KΩ(load)
200MΩ/500V 500KΩ(load)
0~1000MΩ 1mA ≤1mA
/1000V
1000~2000MΩ 1MΩ
/1000V

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5. BATTERY REPLACEMENT
5.1. How to connect test leads.
a) On MΩ Range: Connect the red test lead into the “VΩ” terminal
and the black lead into the “COM” terminal.
b) On 200Ω and ACV Range: Connect the red test lead into the “VΩ”
terminal and the black lead into terminal “COM”
5.2. Battery Check-UP & Replacement
a) As battery power is not sufficient. LCD will display. Replacement of
6 pcs new batteries, type 1.5V size “AA” is required.
b) Place back the battery cover and four the screws.
5.3. Test leads check
Set the range select switch to the 200Ω range. With the tip
and alligator clip of the test leads connected. The indicator
should read 00.0Ω. When the leads are not connected the
display will read infinity indicated by “1”. This will ensure that
test lead are under working condition.
4. PARTS & CONTROLS
1. Digital Display
2. Data Hold Button
3. Lock Button
4. Backlight Button
5. Test Button
6. Rotary Function switch
7. VΩ Jack
8. COM input jack
9. Pothook
10. Battery Cover

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6. INSULATION RESISTANCE MEASUREMENTS
6.1. Measurements at 200MΩ/250V
This is the voltage used for the majority of insulation resistance tests on
normal installation requirement. To measure insulation resistance, press
the test button to power on the tester. The LCD will displayed the
insulation resistance. Section VII indicated that subdivision of large
installations might be necessary because of the large number of parallel
insulation resistance. In such a case, an installation may be divided into
sections, each being separately tested. Each section must have not less
than fifty outlets, an outlet being a switch, socket, lighting point etc. A
switched socket counts as one outlet. The minimum acceptable
insulation resistance is 1MΩ. For a large installation, the capacitance of
the insulation will be high, and it will take longer for it to become
charged by the direct testing voltage. Care must be taken not to take a
reading until there is a steady reading, indicating that the charging
process is complete.
Note: The charge stored in the insulation will be discharged
automatically when the test button is released. Be careful not to turn
the range switch knob whilst the test button is pressed, or the
instrument will be damaged.
6.2. Measurements at 2000MΩ/1000V
Some specifications require testing at 1000V. This voltage must also be
selected where the supply voltage of the installation is between 500V
and 1000V. First, set the range switch to 1000V and then proceed as
indicated in a above for 500V testing. The above note also applies to
testing at 1000V. In addition the following applies.
Note: Make sure that the circuit under does not include components
Which will be damaged by the 1000V applied. Many normal components
of an installation are likely to be damaged if tested at 1000V. Examples
are power factor correction capacitors, low voltage mineral insulated
cables, electronic light dimmers, electronic ballasts and starters for
fluorescent lamps etc…
6.3. Lock power on Feature
For hands free operation a lock power on feature is incorporated on the
press to test button. Set LOCK button to lock test voltage, Pressing it
again will switch it off.

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7. LOW RESISTANCE (CONTINUITY) MEASUREMENTS
1. Set the range switch to 200Ω Position
2. Connect the red test lead to the V Ω terminal and black to the COM
terminal.
3. Connect the tips of the test leads to both ends of the circuit under
test read resistance in Ω on the LCD.
4. When the impedance on circuit is below approximately 40Ω. It will
indicate by a continuous beeper.
8. AC/DC VOLTAGE MEASUREMENTS
1. Set the range switch to ACV or DCV position
2. Connect red test lead to “V Ω” terminal and black test lead to terminal
“COM”.
3. Connect test prods of test leads IN PARALLEL to the circuit being
measured.
4. Read the voltage value on LCD.
9. POWER TOOLS AND SMALL APPLIANCES
This test would also apply to other similar equipment that has a line cord.
For double insulated power tools, the megohmmeter lead shown connected
to the housing would be connected to some metal part lf the tool
(e.g. chuck,blade).
Note: The switch of the device must be in the “ON” position and the main
power should be disconnected.
MOTORS
AC-Disconnect the motor from the line by disconnecting the wires at the
motor terminals or by opening the main switch. If the main switch is used
and the motor also has a starter then the starter must be held, by some
means, in the “ON” position. In the latter case, the measured resistance
will include the resistance of the motor, wire and all other components
between the motor and the main switch. If a weakness is in dicated, the
motor and other components should be checked individually. If the motor is
disconnected at the motor terminals, connect one megohmmeter lead to
the grounded motor housing and the other lead to One of the motor leads.
DC-Disconnect the motor from the line. To test the brush rigging, field coils
and armature connect one megohmmeter lead to the grounded motor
housing and the other lead to the brush on the commutator. If the
resistance measurement indicates a weakness, raise the brushes off the
commutator and separately test the armature, field coils and brush rigging
by connecting one megohmmeter lead to each of them individually, leaving
the other connected to the grounded motor housing. The above also
applies to DC Generators.

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CABLES
Disconnect the cable from the line. Also disconnect opposite end to avoid
errors due to leakage from other equipment. Check each conductor to
ground and /or lead sheath by connecting one megohmmeter lead to a
ground and /or lead sheather and the other megohmmeter lead to each
of the conductors in turn. Check insulation resistance between conductors
by connecting megohmmeter leads to conductors in pairs.

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