Extech Instruments MN45 User manual

User's Guide
Digital Multimeter
Model MN42

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Introduction
Congratulations on your purchase of the Extech MN42 MultiMeter. The MN42 offers AC/DC
Voltage, DC Current, and Resistance testing. Proper use and care of this meter will provide
many years of reliable service.
Safety
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 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 with respect to earth
ground exceeds 600VAC 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.
SAFETY INSTRUCTIONS
This meter has been designed for safe use, but must be operated with caution. The rules
listed below must be carefully followed for safe operation.
1. NEVER apply voltage or current to the meter that exceeds the specified maximum:
Input Protection Limits
Function Maximum Input
V DC or V AC 600V AC and DC 200Vrms on the 200mV range
mA DC 200mA DC 250V fast acting fuse
ADC 10A 250V fast acting fuse
(30 seconds max every 15 minutes)
Resistance, Continuity 250Vrms 15 seconds max
2. USE EXTREME CAUTION when working with high voltages.
3. DO NOT measure voltage if the voltage on the "COM" input jack exceeds 500V above
earth ground.
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 power and disconnect test leads before opening the covers to replace
the fuse or battery.
7. NEVER operate the meter unless the back cover and 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.
WARNING
CAUTION
MAX
600V

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Controls and Jacks
1. Non-Contact Voltage Sensor
2. LCD Display
3. Function switch
4. Positive jack
5. COM jack
6. 10A jack
Note: Tilt stand, fuse, and battery compartment
are on rear of unit.
Symbols
•))) Continuity
Diode
µ micro (amps)
m milli (volts, amps)
k kilo (ohms)
Ω Ohms
Alternating (AC) current
Direct (DC) current
BAT Battery test
+
-
Low battery icon
2
3
4
5
6
1

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Operating Instructions
NON-CONTACT VOLTAGE (NCV)
WARNING: Always test the NCV function on a know live circuit before use
1. Turn the rotary switch to any measurement position
2. Hold the top of the meter very close to the voltage source as shown.
3. If voltage is present, the LED above the display will glow and the
meter will buzz.
NOTE: The detector is designed with high sensitivity. Static electricity or
other sources of energy may randomly trip the sensor. This is normal
operation.
AC VOLTAGE MEASUREMENTS
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 jack.
Insert red test lead banana plug into the positive V 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 circuit.
4. Read the voltage in the display.

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DC VOLTAGE MEASUREMENTS
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 jack.
Insert the red test lead banana plug into the positive Vjack.
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. Move the function switch to
successively lower VDC positions to obtain a higher resolution
reading. The display will indicate proper decimal point and value.
If the polarity is reversed, the display will show (-) minus before
the value.
DC CURRENT MEASUREMENTS
CAUTION: Do not make current measurements at 10 Amps 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 negative COM jack.
2. For current measurements up to 200mA DC, set the function
switch to the highest mADC position and insert the red test lead
banana plug into the mA jack.
3. For current measurements up to 10A DC, set the function switch
to the 10A DC range and insert the red test lead banana plug into
the 10A 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. For mADC measurements, reset
the function switch to successively lower mADC positions to
obtain a higher resolution reading.
+
-
+-

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RESISTANCE MEASUREMENTS
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
jack.
Insert the red test lead banana plug into the positive Ωjack.
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. Move the function switch to
the lowest Ωposition that is greater than the anticipated
resistance.
CONTINUITY CHECK
WARNING: To avoid electric shock, never measure continuity on circuits that have a
voltage potential.
1. Set the function switch to the position.
2. Insert the black lead banana plug into the negative COM jack.
Insert the red test lead banana plug into the positive Ωjack.
3. Touch the test probe tips to the circuit or wire you wish to check.
4. If the resistance is less than approximately 30Ω, the audible signal
will sound. If the circuit is open, the display will indicate “1”.

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DIODE TEST
1. Set the function switch to the position.
2. Insert the black test lead banana plug into the negative COM jack
and the red test lead banana plug into the positive jack.
3. Touch the test probes to the diode under test.
4. Forward voltage will indicate 400 to 700mV.Reverse voltage will
indicate “1”.
5. A shorted diode will indicate the same value of resistance in both
the reverse and forward test directions. Shorted diodes will
indicate near 0mV. An open diode will indicate “1” in both test
directions.
BATTERY TEST
CAUTION: Do not measure batteries while they are installed in the devices they are
powering. The batteries must be removed from installations before tests can be made.
1. Set the function switch to the 1.5V or 9V BAT switch position.
Use the 1.5V position for ‘AAA’, ‘AA’, ‘C’, ‘D’, and other 1.5V
batteries. Use the 9V position for square 9V transistor batteries.
2. Insert the black test lead banana plug into the negative COM jack.
Insert the red test lead banana plug into the positive Vjack.
3. Touch the black test probe tip to the negative side of the battery.
Touch the red test probe tip to the positive side of the 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
►

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Maintenance
WARNING: To avoid electric shock, disconnect the test leads from any source of voltage
before removing the back cover or the battery or fuse covers.
WARNING: To avoid electric shock, do not operate your meter until the battery and fuse
covers are in place and fastened securely.
This MultiMeter is designed to provide years of dependable service, if the following care
instructions are performed:
1. KEEP THE METER DRY. If it gets wet, wipe it off.
2. USE AND STORE THE METER IN NORMAL TEMPERATURES. Temperature
extremes can shorten the life of the electronic parts and distort or melt plastic parts.
3. HANDLE THE METER GENTLY AND CAREFULLY. Dropping it can damage the
electronic parts or the case.
4. KEEP THE METER CLEAN. Wipe the case occasionally with a damp cloth. DO
NOT use chemicals, cleaning solvents, or detergents.
5. USE ONLY FRESH BATTERIES OF THE RECOMMENDED SIZE AND TYPE.
Remove old or weak batteries so they do not leak and damage the unit.
6. IF THE METER IS TO BE STORED FOR A LONG PERIOD OF TIME, the battery
should be removed to prevent damage to the unit.
BATTERY INSTALLATION and LOW BATTERY INDICATION
LOW BATTERY INDICATION
The
+
-
icon will appear in the display when the battery voltage becomes low. Replace the
batteries when this appears.
BATTERY REPLACEMENT
1. Disconnect the test leads from the meter.
2. Remove the Phillips head screws (2) which secure the rear battery compartment
cover.
3. Remove the fuse/battery compartment cover to access the battery.
4. Replace the 9V battery, observing polarity.
5. Replace and secure the fuse/battery compartment cover .
You, as the end user, are legally bound (Battery ordinance) to return all used
batteries and accumulators; disposal in the household garbage is prohibited!
You can hand over your used batteries / accumulators at collection points in your
community or wherever batteries / accumulators are sold!
Disposal: Follow the valid legal stipulations in respect of the disposal of the
device at the end of its lifecycle
REPLACING THE FUSES
1. Disconnect the test leads from the meter.
2. Remove the Phillips head screws (2) which secure the rear battery compartment
cover.
3. Remove the fuse/battery compartment cover to access the fuses.
4. Gently remove the fuse(s) and install new fuse(s) into the holder(s).
5. Always use fuses of the proper size and value (0.2A/250V fast blow for the 200mA
range, 10A/250V fast blow for the 10A range).
6. Replace and secure the fuse/battery compartment cover .

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Range Specifications
Function Range Resolution Accuracy
DC Voltage
(V DC)
200mV 0.1mV
±(0.5% reading + 2 digits)
2000mV 1mV
20V 0.01V
200V 0.1V
±(0.8% reading + 2 digits)
600V 1V
AC Voltage
(VAC) 50/60Hz
200V 0.1V ±(1.2% reading + 10 digits)
600V 1V ±(2.0% reading + 4 digits)
DC Current
(A DC)
2000µA 1µA
±(1.0% reading + 2 digits)
20mA 10µA
200mA 100µA ±(1.5% reading + 2 digits)
10A 10mA ±(2.0% reading + 2 digits)
Resistance 200Ω0.1Ω
±(0.8% reading + 2 digits)
2000Ω1Ω
20kΩ0.01kΩ
200kΩ0.1kΩ
2000kΩ1kΩ±(1.0% reading + 2 digits)
Battery Test 9V 10mV
±(1.0% reading + 2 digits)
1.5V 10mV
Notes:
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.
Accuracy is stated at 65oF to 83oF (18oC to 28oC) and less than 75% RH.

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General Specifications
Diode Test Test current of 1mA max, open circuit voltage 2.8VDC typical.
Continuity Check Audible signal will sound if the resistance is less than 30Ω
Batter Test current 9V (6mA); 1.5V (100mA)
Input Impedance >1MΩ
ACV Bandwidth 45Hz to 450Hz
DCA voltage drop 200mV
NCV voltage range 100VAC to 600VAC
Display 3 ½ digit, 2000 count LCD, 0.5” digits
Overrange indication “1” is displayed
Polarity Automatic (no indication for positive); Minus (-) sign for
negative
Measurement Rate 2 times per second, nominal
Low Battery Indication
+
-
is displayed if battery voltage drops below operating
voltage
Battery One (1) 9V battery
Fuses mA, µA ranges; 0.2A/250V fast blow
A range; 10A/250V fast blow
Operating Temperature 0ºC to 50ºC (32ºF to 122ºF`)
Storage Temperature -20oC to 60oC(-4oF to 140oF )
Operating Humidity <70% RH
Storage Humidity < 80% RH
Operating Altitude 2000 meters (7000 ft.) maximum.
Weight 255g(9 oz )
Size 150 x 70 x 48mm (5.9” x 2.75” x 1.8”)
Safety This meter is intended for indoor use and in accordance with
Overvoltage Category III-600V, Pollution Degree 2.
PER IEC1010 OVERVOLTAGE INSTALLATION CATEGORY
OVERVOLTAGE CATEGORY I
Equipment of OVERVOLTAGE CATEGORY I is equipment for connection to circuits in
which measures are taken to limit the transient overvoltages to an appropriate low level.
Note – Examples include protected electronic circuits.
OVERVOLTAGE CATEGORY II
Equipment of OVERVOLTAGE CATEGORY II is energy-consuming equipment to be
supplied from the fixed installation.
Note – Examples include household, office, and laboratory appliances.
OVERVOLTAGE CATEGORY III
Equipment of OVERVOLTAGE CATEGORY III is equipment in fixed installations.
Note – Examples include switches in the fixed installation and some equipment for
industrial use with permanent connection to the fixed installation.
OVERVOLTAGE CATEGORY IV
Equipment of OVERVOLTAGE CATEGORY IV is for use at the origin of the installation.
Note – Examples include electricity meters and primary over-current protection equipment
Copyright ©2010 Extech Instruments Corporation (a FLIR company).
All rights reserved including the right of reproduction in whole or in part in any form.