Major tech MT874 User manual

Operating Instruction for
True RMS Digital Multimeter
Please read this manual before switching the unit on.
Important safety information inside.
MT874
600V AC/DC TRMS
MULTIMETER
INSTRUCTION MANUAL

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1. Safety............................................................................................ 4
1.1. Safety Instructions.................................................................. 4
1.2. Safety Symbols....................................................................... 4
1.3. Input Limits............................................................................. 5
1.4. Safety Category Ratings.......................................................... 5
1.5. Test Leads............................................................................... 5
2. Description.................................................................................... 6
2.1. Meter Description.................................................................... 6
2.2. Symbols Used on LCD Display................................................ 7
3. Specifications................................................................................ 8
3.1. Specifications......................................................................... 8
3.2. General Specifications............................................................ 9
4. Battery Installation......................................................................... 10
5. Button Function............................................................................. 10
5.1. Data Hold Button..................................................................... 10
5.2. Mode/Rel Button..................................................................... 10
5.3. Auto Power Off....................................................................... 10
6. Operating Instructions................................................................... 11
6.1. DC Voltage Measurement....................................................... 11
6.2. AC Voltage Measurement....................................................... 12
6.3. DC Current Measurement....................................................... 13
6.4. AC Current Measurement....................................................... 14
6.5. Resistance Measurement....................................................... 15
6.6. Continuity Check..................................................................... 16
6.7. Diode Test............................................................................... 17
6.8. Battery Test............................................................................. 18
7. Replacing The Battery................................................................... 19
8. Replacing The Fuses.................................................................... 19
Contents Page no

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1. Safety
1.1. Safety Instructions
• This meter has been designed for safe use, but must be operated with
caution.
• The instructions listed below must be carefully followed for safe operation.
1. Never apply voltage or current to the meter that exceeds the specified
maximum:
2. Use extreme caution when working with high voltages.
3. Do not measure voltage if the voltage on the “com” input jack exceeds
600V.
4. Never connect the meter leads across a voltage source while the function
switch is in the current, resistance or diode mode. Doing so can damage
the meter.
5. Always discharge filter capacitors in power supplies and disconnect the
power when making resistance or diode tests.
6. Always turn off the power and disconnect the test leads before opening
the cover to replace the fuse or batteries.
7. Never operate the meter unless the back cover, the battery and fuse
covers are in place and fastened securely.
8. If the equipment is used in a manner not specified by the manufacturer,
the protection provided by the equipment may be impaired.
1.2. Safety Symbols
This symbol adjacent to another symbol, terminal or operating
device indicates that the operator must refer to an explanation in
the Operating Instructions to avoid personal injury or damage to the
meter.
This WARNING symbol indicates a potentially hazardous situation,
which if not avoided, could result in death or serious injury.
This CAUTION symbol indicates a potentially hazardous situation,
which if not avoided, may result in damage to the product.
This symbol advises the user that the terminal(s) so marked must
not be connected to a circuit point at which the voltage exceeds
600 VAC or VDC.
This symbol adjacent to one or more terminals identifies them as
being associated with ranges that may, in normal use, be subjected
to particularly hazardous voltages. For maximum safety, the meter
and its test leads should not be handled when these terminals are
energized.
This symbol indicates that a device is protected throughout by
double insulation or reinforced insulation. This symbol indicates
that a device is protected throughout by double insulation or
reinforced insulation.
MAX

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1.3. Input Limits
Voltage AC or DC 600 V AC/DC, 200Vrms on 200mV range
Resistance, Continuity 250 Vrms for 15 sec max
mA DC or mA AC 200mA 600V fast acting fuse
A DC or A AC 10A 600V fast acting fuse (30 seconds max
every 15 minutes)
• When the measured voltage or current exceeds the range, the buzzer will
continue to sound as a warning of exceeding the range.
1.4. Safety Category Ratings
Category Rating Brief Description Typical Applications
Single phase
receptacles and
connected loads
Three phase circuits
and single phase
lighting circuits in
commercial buildings
CAT II
CAT III
• Household appliances, power
tools
• Outlets more than 30ft (10m)
from a Cat III source
• Outlets more than 60ft (20m)
from a Cat IV source
• Equipment in fixed installations
such as 3- phase motors, switch
gear and distribution panels
• Lighting circuits in commercial
buildings
• Feeder lines in industrial plants
• Any device or branch circuit that
is close to a Cat III source
• The measurement category (CAT) rating and voltage rating is determined by a
combination of the meter, test probes and any accessories connected to the
meter and test probes.
• The combination rating is the LOWEST of any individual component.
1.5. Test Leads
CAT IV 600V
CAT III 1000V
Insulated Tip On
Insulated Tip Removed
WARNING: Operation is limited to CAT II applications when the insulated tips
are removed from one or both test probes. Refer to Input Limits section in this
manual for maximum voltage ratings.

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2.1. Meter Description
1 - LCD Display
2 - MODE/RELATIVE Button
3 - HOLD Button
4 - Function Switch
5 - 10A Input Jack
6 - Positive Input Jack
7 - COM Input Jack
8 - Lanyard Hole
9 - Test Lead Holders
10 - Battery Cover Lock
11 - Tilt Stand
12 - Battery Cover
2. Description

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1 - Auto Power Off
2 - Display Hold
3 - Relative
4 - Diode Test
5 - Continuity
6 - Units of Measure List
7 - Alternating Current
8 - Direct Current
9 - Minus Sign
10 - Battery Status
11 - Measurement Reading
2.2. Symbols Used on LCD Display

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3. Specifications
3.1.Specifications
20V 0.01V
200V ±(0.8% + 5 digits)
0.1V
Range
200mV
2V
Accuracy
±(0.5% + 5 digits)
Function
DC Voltage
Resolution
0.1mV
0.001V
600V 1V
All AC voltage ranges are specified from 5% of range to 100% of range;
AC voltage bandwidth: 50Hz to 1kHz (Sine), 50Hz to 60Hz (All wave).
200V
600V
±(1.2% + 10 digits)
AC Voltage 0.1V
1V
200mA
10A
±(1.2% + 5 digits)
DC Current 0.1mA
0.01A ±(2.0% + 5 digits)
200mA
10A
±(1.2% + 5 digits)
AC Current 0.1mA
0.01A ±(2.0% + 5 digits)
All AC Current ranges are specified from 5% of range to 100% of range;
AC Current bandwidth: 50Hz to 1kHz (Sine), 50Hz to 60Hz (All wave).
20kΩ0.01kΩ
200kΩ
±(1.0% + 5 digits)
0.1kΩ
200Ω
2kΩ±(0.8% + 5 digits)
Resistance 0.1Ω
0.001kΩ
2MΩ0.001MΩ
9V
1.5V
±(1.0% + 5 digits)
Battery Test 0.01V
0.001V
NOTE: Accuracy specifications consist of two elements:
• (% reading) - This is the accuracy of the measurement circuit.
• (+ digits) - This is the accuracy of the analog to digital converter.
NOTE: Accuracy is stated at 18 to 28°C (65 to 83°F) and less than 75% RH.

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3.2. General Specifications
Insulation Class 2, Double insulation.
Diode Test Test current of 1mA maximum, open circuit voltage 2V
DC typical
Continuity Check Audible signal will sound if the resistance is less than
approximately 50Ω
Battery Test current 9V (6mA); 1.5V (100mA)
Input Impedance Approximately 10MΩ (VDC and VAC)
AC Response True RMS
ACA Bandwidth 50Hz to 1kHz
ACV Bandwidth 50Hz to 1kHz
Display 3 ½ digit, 2000 count LCD
Overrange indication “OL” is displayed
Polarity Automatic (no indication for positive polarity); Minus
(-) sign for negative polarity.
Measurement Rate 2 times per second, nominal
Low Battery Indication “ ” is displayed if battery voltage drops below
operating voltage
Battery Two 1.5V “AAA” batteries
Auto Power Off Approximately 15 minutes
Fuses mA, μA ranges: 200mA/600V fast blow; A range:
10A/600V fast blow
Operating Temperature 0 to 50°C (32 to 122°F)
Storage Temperature -10 to 60°C (14 to 140°F)
Relative Humidity <70% operating, <80% storage
Operating Altitude 7000ft. (2000) meters maximum.
Safety For indoor use and in accordance with Overvoltage
Category II, Pollution Degree 2. Category II includes
local level, appliance, portable equipment, etc., with
transient overvoltages less than Overvoltage
Category III. Probe assemblies to be used for mains
measurements shall be rated as
appropriate for measurement Category III according
to IEC 61010-31 and shall have a voltage rating of at
least the voltage of the circuit to be measured.
Measurement category III (CAT III) is applicable to
test and measuring circuits connected to the
distribution part of the building’s low-voltage mains
installation.

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4. Battery Installation
WARNING: To avoid electric shock, disconnect the test leads from any source
of voltage before removing the battery cover.
1. Disconnect the test leads from the meter.
2. Open the battery cover by loosening the screw using a Flat head
screwdriver.
3. Insert the battery into battery holder, observing the correct polarity.
4. Put the battery cover back in place, secure with the screw.
WARNING: To avoid electric shock, do not operate the meter until the battery
cover is in place and fastened securely.
NOTE: If your meter does not work properly, check the fuses and batteries to
make sure that they are still good and that they are properly inserted.
5. Button Function
5-1. Data Hold Button
The Data Hold function allows the meter to “freeze” a measurement for later
reference.
1. Press the Data Hold Button to “freeze” the reading on the indicator, the
indicator “H” will be appear in the display.
2. Press the Data Hold Button to return to normal operation.
5-2. Mode/Rel Button
1. Under the Diode Test/Continuity Check, press Mode/Rel Button for select
function.
2. Under Voltage/Current/Resistance measurements, pressing Mode/Rel
Button is REL function.
5-3. Auto Power Off
• The auto off feature will turn the meter off after 15 minutes.
• To disable the auto power off feature, hold down the Mode/Rel Button and
turn the meter on.
Note: The above data only for reference.

6. Operating Instructions
WARNING: Risk of electrocution. High-voltage circuits, both AC and DC, are
very dangerous and should be measured with great care.
• Always turn the function switch to the OFF Position when the meter is not in
use.
• If “OL” appears in the display during a measurement, the value exceeds the
range you have selected. Change to a higher range.
NOTE: On some low AC and DC voltage ranges, with the test leads not
connected to a device, the display may show a random, changing reading. This
is normal and is caused by the high-input sensitivity. The reading will stabilize
and give a proper measurement when connected to a circuit.
CAUTION: Do not measure DC voltages if a motor on the circuit is being
switched ON or OFF. Large voltage surges may occur that can damage the
meter.
1. Set the function switch to
the highest VDC Position.
2. Insert the black test lead
banana plug into the
negative COM Input Jack;
Insert the red test lead
banana plug into the
Positive Input Jack.
3. Touch the black test probe
tip to the negative side of
the circuit; Touch the red
test probe tip to the positive
side of the circuit.
4. Read the voltage in the
display.
5. Reset the function switch to
successively lower VDC
Position to obtain a higher
resolution reading, the
display will indicate the
proper decimal point and
value.
6. If the polarity is reversed,
the display will show (-) minus before the value.
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6.1. DC Voltage Measurement

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6.2. AC Voltage Measurement
WARNING: Risk of Electrocution. The probe tips may not be long enough
to contact the live parts inside some 240V outlets for appliances because
the contacts are recessed deep in the outlets. As a result, the reading may
show 0 volts when the outlet actually has voltage on it. Make sure the
probe tips are touching the metal contacts inside the outlet before
assuming that no voltage is present.
CAUTION: Do not measure AC voltages if a motor on the circuit is being
switched ON or OFF. Large voltage surges may occur that can damage the
meter.
1. Set the function switch to the highest VAC Position.
2. Insert the black test lead banana plug into the negative COM Input Jack;
Insert the red test lead banana plug into the Positive Input Jack.
3. Touch the black test probe tip to the negative side of the circuit; Touch
the red test probe tip to the positive side of the circuit.
4. Read the voltage in the display.
5. Reset the function switch to successively lower VAC Position to obtain a
higher resolution reading, the display will indicate the proper decimal
point and value.

CAUTION: Do not make current measurements on the 10A scale for longer
than 30 seconds. Exceeding 30 seconds may cause damage to the meter
and/or the test leads.
1. Insert the black test lead banana plug into the COM Input Jack.
2. For current measurement up to 200mA DC, set the function switch to
the highest DC mA Position and insert the red test lead banana plug
into the Positive Input Jack.
3. For current measurement up to 10A DC, set the function switch to the
10A range and insert the red test lead banana plug into the 10A Input
Jack.
4. Remove power from the circuit under test, then open up the circuit at the
point where you wish to measure current.
5. Touch the black test probe tip to the negative side of the circuit; Touch
the red test probe tip to the positive side of the circuit.
6. Apply power to the circuit.
7. Read the current in the display.
8. For mA DC measurements, reset the function switch to successively
lower mA DC position to obtain a higher resolution reading, the display
will indicate the proper decimal point and value.
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6.3. DC Current Measurement

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CAUTION: Do not make current measurements on the 10A scale for longer
than 30 seconds. Exceeding 30 seconds may cause damage to the meter
and/or the test leads.
1. Insert the black test lead banana plug into the COM Input Jack.
2. For current measurements up to 200mA AC, set the function switch to
the 200mA AC Position and insert the red test lead banana plug into the
Positive Input Jack.
3. For current measurements up to 10A AC, set the function switch to the
10A range and insert the red test lead banana plug into the 10A Input
Jack.
4. Remove power from the circuit under test, then open up the circuit at the
point where you wish to measure current.
5. Touch the black test probe tip to the negative side of the circuit; Touch
the red test probe tip to the positive side of the circuit.
6. Apply power to the circuit.
7. Read the current in the display, the display will indicate the proper
decimal point and value.
6.4. AC Current Measurement

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WARNING: To avoid electric shock, disconnect power to the unit under test
and discharge all capacitors before taking any resistance measurements.
1. Set the function switch to the highest Ω Position.
2. Insert the black test lead banana plug into the negative COM Input Jack;
Insert the red test lead banana plug into the Positive Input Jack.
3. Touch the test probe tips across the circuit or part under test, it is best to
disconnect one side of the part under test so the rest of the circuit will not
interfere with the resistance reading.
4. Read the resistance in the display and then set the function switch to the
lowest Ω Position that is greater than the actual or any anticipated
resistance, the display will indicate the proper decimal point and value.
6.5. Resistance Measurement

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WARNING: To avoid electric shock, never measure continuity on circuits or
wires that have voltage on them.
1. Set the function switch to the Position.
2. Insert the black test lead banana plug into the negative COM Input
Jack; Insert the red test lead banana plug into the Positive Input Jack.
3. Press the Mode/Rel Button to indicate “ ” and “Ω” on the display
4. Touch the test probe tips to the circuit or wire you wish to check.
5. If the resistance is less than approximately 50Ω, the audible signal will
sound; If the circuit is open, the display will indicate “OL”.
6.6. Continuity Check

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1. Set the function switch to the Position.
2. Insert the black test lead banana plug into the negative COM Input Jack;
Insert the red test lead banana plug into the Positive Input Jack.
3. Press the Mode/Rel Button until “ ” and “V” appears in the display.
4. Touch the test probes to the diode under test. Forward voltage will
indicate 0.4V to 0.7V. Reverse voltage will indicate “OL”. Shorted
devices will indicate near 0mV. Shorted devices will indicate near 0mV
and an open device will indicate “OL” in both polarities.
6.7. Diode Test

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1. Insert the black test lead banana plug into the negative COM Input Jack;
Insert the red test lead banana plug into the Positive Input Jack.
2. Select the 1.5V or 9V BAT Position using the function select switch.
3. Connect the red test lead to the positive side of the 1.5V or 9V battery
and the black test lead to the negative side of the 1.5V or 9V battery.
4. Read the voltage in the display.
Good Weak Bad
9V battery >8.2V 7.2 to 8.2V <7.2V
1.5V battery >1.35V 1.22 to 1.35V <1.22V
6.8. Battery Test

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WARNING: To avoid electric shock, disconnect the test leads from any
source of voltage before removing the battery cover.
1. When the batteries become exhausted or drop below the operating
voltage, “ ” will appear in the LCD display, the batteries should be
replaced.
2. Contrarotate 180 degrees to open the back cover of battery.
3. Replace old batteries with two “AAA” 1.5V batteries.
4. Re-assemble the meter.
5. Dispose of the old batteries properly.
WARNING: To avoid electric shock, do not operate your meter until the
battery cover is in place and fastened securely.
WARNING: To avoid electric shock, disconnect the test leads from any
source of voltage before removing the fuse cover.
1. Disconnect the test leads from the meter and any item under test.
2. Open the fuse cover by loosening the screw on the cover using a Phillips
head screwdriver.
3. Remove the old fuse from its holder by gently pulling it out.
4. Install the new fuse into the holder.
5. Always use a fuse of the proper size and value (200mA/600V fast blow
for the 200mA range,10A/600V fast blow for the 10A range).
6. Put the fuse cover back in place. Insert the screw and tighten it securely.
WARNING: To avoid electric shock, do not operate your meter until the fuse
cover is in place and fastened securely.
• Keep the meter dry, if it gets wet, wipe it off.
• Keep the meter clean. Wipe the case occasionally, do not use chemicals,
cleaning solvents, or detergents.
• Handle the meter gently and carefully, dropping it can damage the
electronic parts or the case.
• Use and store the meter in normal temperatures, temperature extremes
can shorten the life of the electronic parts and distort or melt plastic parts.
• Use only fresh batteries of the recommended size and type, remove old
or weak batteries so they do not leak and damage the unit.
• If the meter is to be stored for a long period of time, the battery should be
removed to prevent damage to the unit.
7. Replacing The Battery
8. Replacing The Fuses
9. Care and Maintenance

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