Congratulations on your purchase of the MG320 True RMS Insulation Resistance CAT IV 600V DMM.
The MG320 features a rugged design for heavy duty use. The MG320 measures Insulation
Resistance, AC/DC Voltage, and Resistance.
Insulation Resistance tests are automatic ranging with 5 test voltages from 50V to 1000V. The
MG320 can store and recall up to 99 measurements.
The MG320 is suitable for measuring the insulation resistance on elecrical equipment such as
transformers, motors, cables, switches, and appliances.
Proper use and care of this meter will provide years of reliable service.
Features
True RMS AC/DC Voltage Measurments to 600V
Insulation Resistance Measurements up to 20
Low Resistance/Continuity Measurements to 20k
Auto Ranging measurements
Polarization Index (PI) and Dielectric Aborption Ratio (DAR)
Five (5) Insulation Resistance test voltages (50, 100, 250, 500, and 1000V)
Insulation Resistance tests in10% voltage steps (from 50% to 120% of range)
Optional remote test probe for controlling the TEST button remotely
Test leads, alligator clips, batteries, user manual, and case included
test voltage alert lamp
nction
mbols
readings
G
tests
2. Safety
Warning and Caution safety label
Double Insulation
DC Direct Current
AC Alternating Current
Low Battery
Fuse symbol
High Voltage Alert
Audible beeper
Earth ground
Complies with EC standard
3 MG320-en-GB_v1.1 1/17
Page 4
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 over-voltages 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
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.
2. USE EXTREME CAUTION when working with high voltages.
3.
OT measure voltage if the voltage on the "COM" input jack exceeds 600V ab
DO N
ove earth
ground.
4. NEVER connect the meter leads
resistance mode. Doing so can damage the mete
5. AL
WAYS discharge filter capacitors in power supplies and disconnect the power when
esistance tests.
r
WAYS turn off the power and disconnect the test leads before opening the covers
6. AL
the fuse or batt
7. NEVER operate
8.
If the equipment is used in a manner not specified by the manufacturer, the protection provided by
eries.
the meter unless the battery/fuse cover is in place and fastened securely.
across a voltage source while the function sw
r.
itch is in the
making
to replace
the equipment may be impaired.
4 MG320-en-GB_v1.1 1/17
Page 5
SAFETY STANDARDS
This instrument is designed and produced strictly in accordance with the safety requirements for GB4793 electronic
measuring instruments and IEC61010-1 safety standards. This instrument meets the double insulation over-voltage
standard CAT IV 600V and pollution degree II. Failure to use the instrument as described in this user manual can
weaken or negate the protections provided.
Check the instrument, test leads, and test pen before use. Check for any abnormal conditions such as
exposed test lead wire, damaged meter housing, no display or random display errors.
Do not use this instrument with an open battery compartment.
Damaged test leads must be replaced with those of the same type or specifications.
Do not touch bare wires or conductors, unused input terminals, or the circuit being measured when the
instrument is in operation.
Use caution when measuring voltages greater than 42V DC or 30V AC. Keep fingers behind the finger guard
on the test leads to avoid electrical shocks when measuring.
Do not apply signals greater than those specified between any two terminals or any terminal and ground.
Set the function switch to the correct position before beginning a test. Never move the function switch during a
test. Please stop testing and remove connections to the circuit under test before moving the function switch to
a new position.
Do not store or use the instrument in an explosive or flammable environment or an environment characterized
by high temperature, high humidity, or strong electromagnetic fields.
There are no user-serviceable parts in this instrument. Please refer all service and repairs to Extech
Instruments.
Replace the batteries as soon as the low battery icon appears in order to ensure the highest measurement
accuracy.
3. MeterDescription
1. 5999 count backlit LCD display with bargraph
2. Control buttons; detailed in next section
3. Rotary function switch
4. Low Resistance/Continuity (+) positive input jack
5. Low Resistance/Continuity (-) COM input jack
6. Insulation and Voltage (-) COM input jack
7. Insulation and Voltage (+) positive input jack
8. Test Voltage alert LED indicator
Note: Tilt stand and battery compartment on back
1
2
8
3
4
5
5 MG320-en-GB_v1.1 1/17
7
6
Page 6
4. Controlbuttons
1.Data Hold on/off (short press) for AC/DC Voltage and Resistance modes only. Also for display
Backlight on/off (long press)
Short press to Recall stored readings. Another short press to ex
2.
Save reading (short press) and Clear all stored read
3.
4.
Comparator (short press) and Zero (long press)
5.PI and DAR test mode selection (short
pr
esses)
6.
Insulation Test Lock button (long
activate/deactivate lock mode)
Up arrow for adjusting test voltage
7.
scrolling through recalled readings
Down arrow for adjusting test volt
8.
and scrolling through recalled readings
Press to start Insulation or Low Re
9.
tests. Insulation t
tests can be made up to 20kΩ.
ests output high voltages and measure insulation resistance. Low Re
press to
output and
age output
sistance
ings (long press)
3
2
1
it this mode.
45
9
sistance
5. SymbolsandAnnunciators
6
7
8
1. Test Voltage alert
2. Insulation Test Lock icon
Audible beeper symbol
3.
PI/DAR test mode
4.
5.
True RMS voltage measurement
6.
7. Batter
8. Test voltage value
9.
10.
11.
12.
13.
14.
15.
function icon
ZERO
y status
Measurement ty
PI/DAR timer information
Bargraph measurement represent
Comparator area: Test pass [PASS], test fail [NG], units [K, M, G], and refe
Main measurement display digits
Display Hold Icon (freeze/unfreeze display)
Save/Recall readings (01-99)
s
pe and units
ation
15
14
13
12
1234567
6 MG320-en-GB_v1.1 1/17
8
9
10
11
rence value.
Page 7
6. OperatingInstructions
WARNING: Risk of electrocution. High-voltage circuits, both AC and DC, are very dangerous and should be
measured with great care.
1. ALWAYS turn the function switch to the OFF position when the meter is not in use.
2. If “>” appears in the display during a measurement, the value exceeds the maximum range of
the meter.
6.1 Display Backlight
Press and hold the button to switch the backlight on or off. Excessive use of the backlight will
cause the batteries to drain quicker.
6.2 Data Hold
The Data Hold function freezes the reading in the display. To freeze or unfreeze the reading, press
H (Data Hold) key. The H icon is shown when data hold is active. This mode is available for Voltage
and Resistance modes only.
6.3 Low Battery Indication
When the icon appears in the display, the battery must be replaced. See the Maintenance
section for details on battery and fuse replacement.
6.4 DC VOLTAGE MEASUREMENTS
CAUTION:
When the measured voltage is > 42VDC or 600VAC the meter flashes the warning icon on the upper left.
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 position.
2. Insert the black test lead banana plug into the negative COM jack (6).
Insert the red test lead banana plug into the positive V jack (7).
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 main display and in the lower bargraph.
5. Press the
button to store the reading.
6. Short press the H (Hold) button to freeze (H icon displayed) or
unfreeze (no H icon displayed) the displayed reading.
7. Note that the Auto Power OFF function activates after 3 minutes of
inactivity. The meter will audibly beep just prior to shutting off.
7 MG320-en-GB_v1.1 1/17
100 200 300 400 500 600 700
0
V
DC
Page 8
6.5 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.
Do not measure voltages higher than 600V
When the measured voltage is > 60VDC or 600VAC the meter flashes the warning icon on the upper left.
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 position.
2.Insert the black test lead banana plug into the negative COM
(6).
Insert red test le
Touch the black test probe tip to the neutral side of
3.
Touch the r
4.
Read the voltage in the main display and in the lower bargr
5.
Short press the H (Hold) button to freeze (H icon displayed)
unfreeze (n
6. Press
7.
Note that the Auto Power OFF function activates af
of inactivity
8.
Note that the Auto Power OFF function activates af
ad banana plug into the positive V jack
the circuit.
ed test probe tip to the “hot” side of the circuit.
o H icon displayed) the displayed reading
to store the reading
ter 3 minutes
. The meter will audibly beep just prior to
shutting off.
ter 3 minutes
of inactivity. The meter will audibly beep just prior to shutting off.
jack
V
(7).
100 200 300 400 500 600 700
0
AC
aph.
or
.
8 MG320-en-GB_v1.1 1/17
Page 9
6.6 LOW RESISTANCE/CONTINUITY MEASUREMENTS
WARNING: To avoid electric shock, disconnect power to the unit under test and discharge all capacitors
before taking any resistance measurements. Remove the batteries and unplug the line cords.
WARNING: To avoid electric shock, never measure resistance on circuits or wires that have a voltage.
1.Set the function switch to the Ω position.
2.
Insert the black test lead banana plug into the negative COM
(5).
jack
Insert the re
CONTINUI
3. Press
remote test leads
will show TEST and the front panel alert LED will lig
Reset the display to zero before testing: Short the te
4.
and note the valu
hold ZERO until ZERO is displa
successfu
Before testing, it is best to discon
5.
under test so tha
resistance reading.
Touch the test probe tips across the circuit or part under test.
6.
7.Read the resistance in the main display.
If the circuit is open, the display will indicate “>”. If 2V
8.
are sensed on th
test.
Short press the H (Hold) button to freeze (H icon displayed) or unfreeze (no H icon displayed)
9.
the displayed read
10. Press
11.
Note that the Auto Power OFF function activates after 3 minutes of inactivity. The meter w
audibl
d test lead banana plug
TY jack
(4).
the TEST button on the meter (or on the
) to put the meter in test mode. The display
e. Short the test probes again an
l). Press and hold ZERO again to exit.
t other circuits do not interfere with
e device under test, the meter w
ing.
to store the reading
y beep just prior to shutting
into the positive
yed (0.00Ω reading
nect one side of the part
off.
optional
ht.
st probes
d press and
when
the
or more
ill stop the
TEST
>
ill
99 Washington Street
Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
9 MG320-en-GB_v1.1 1/17
Page 10
6.7 INSULATION RESISTANCE MEASUREMENTS
Note: Disconnect the unit under test from all power sources and isolate it from any stray
resistance.
1.Connect the red test lead to the meter’s INSULATION (+) jack (7) and the black test lead to the
EA
RTH (-) jack (6). Connect the probe end of the te
2.
Set the rotary function switch to one of t
250V, 500V, or
3. Press
4.
5.
6.
7. Press
8.
9.
10. Press
the TEST button on the meter (or on the optional remote test lead) to start testing (TEST
will display)
The primary display and the analog bargraph will show
the insulation resistance in Ω
The test voltage (VDC) value w
right display
r
ed LED w
The meter defaults to test lock mo
ed) so the test will run wi
display
TEST button
the TEST button to stop th
At the end of each test the high voltage switches off
(alert symbol
resistance value is held in the primary display, and
meter internall
voltage.
Short press the H (Hold) button to freeze (H icon)
unfreeze (no
1000V); the selected test voltage is indicated on the top right of the display.
.
.
symbol will flash and the front panel
, the
ill light.
.
and LED light switch off), the measured
scharges the balance of the test
y di
H icon) the displayed
to store the reading
he Insulation Resistance test positions (50V, 100V,
ill be indicated in the top
de (lock icon
thout having to hold the
e test.
reading.
st leads to the circuit under test.
the
or
Note: If the circuit under test is live and has a voltage potential (AC/DC) over 25V, the meter will not
test (the display will show “EXT” and the
its voltage is less than 25V, the meter will begin applying voltage to the circuit under test.
Note: Do not turn the function switch to another test position during a test. Please wait until a test is
completed and test leads are removed from the device under test before moving the function switch.
symbol will flash). If the circuit under test is not live or if
6.7.1 Disable Insulation Test Lock Mode
To disable test lock mode, press and hold the button until the lock icon switches off and
then press and hold the TEST button for the duration of the test (TEST will be displayed).
Release the button to stop the test.
10 MG320-en-GB_v1.1 1/17
Page 11
6.7.2 Insulation Resistance Test Time Setup
1. Press the button to select the desired test time. Select from 15s, 30s, 1m, 15s/1m,
1m/30s, 10m, 15s/10m, and 30s/10m. Connect the meter to the device under test as shown
in the Insulation Resistance test section above.
2. Press TEST to start the test. The test will end automatically after the time period has elapsed.
NOTE: Combination test times (15s/1m, for example) provide an audible beep at the first test time
value and then continue testing until the test automatically stops at the second test time value.
6.7.3 Dielectric Absorption Ratio [DAR] Insulation Testing
Read and understand all operations and safety information in the Insulation Resistance
measurement section above and in the Safety section before continuing.
1. Connect the meter to the device under test as shown in the Insulation test section above.
2. Select the desired output test voltage using the rotary function switch.
3. Use the PI/DAR button to step to the first DAR test mode (60 seconds : 15 seconds ratio test)
or to the second DAR test mode (60 seconds : 30 seconds ratio test).
4. The display will show the DAR icon when the DAR mode is successfully accessed.
5. The test times will show on the lower right.
6. Press the TEST button to start the test. When Time1 is reached the meter beeps and then
beeps again when Time2 is reached at which time the test automatically stops.
7. During the test the main display digits show the test elapsed timer, the voltage alert flashes
on the upper left, and the ‘test voltage alert’ LED will light.
8. If the insulation breaks down during the test, the meter emits an audible tone and buzzer.
9. Press the TEST button to stop the test and activate the discharging circuit.
6.7.4 Polarization Index [PI] Insulation Testing
Read and understand all operations and safety information contained in the Insulation Resistance
measurement section above and the Safety section before continuing.
1. Connect the meter to the device under test as shown in the test section above.
2. Select the desired output test voltage using the rotary function switch.
3. Use the PI/DAR button to access the PI test mode.
4. The display will show the PI icon when the PI mode is successfully accessed.
5. The timers (Time1: 60 seconds and Time2: 10 minutes) will show on the lower right.
6. Press the TEST button to start the test.
7. After 60 seconds (Time1) the meter beeps. The meter beeps again at the 10 minute mark
(Time2) after which the test automatically stops.
8. During the test the main display digits show the test elapsed timer, the voltage alert flashes
on the upper left, and the ‘test voltage alert’ LED illuminates.
9. If the insulation breaks down during the test, the meter emits audible tone and buzzer.
10. Press the TEST button to stop the test and activate the discharging circuit.
11 MG320-en-GB_v1.1 1/17
Page 12
6.7.5 Comparator Utility
Read and understand all operations and safety information contained in the Insulation Resistance
and Continuity measurement sections and the Safety section before continuing.
In Comparator mode the meter compares measurement to a preset reference values and
displays PASS (measured value greater than reference value) or NG (measured value lower than
reference value).
Connect the meter to the device under test as shown in th
1.
2. Press
3. Press
4.
5.
the COMP button momentarily and the COMP icon will appear on the lower left, nex
the comparison
the TEST button to start the test. If the measurement is greater than the refer
then the test pas
reference th
The Continuity comparator preset options are: 1, 2, 5, 10, and 20Ω
resistance value. Use the COMP button to step to the desired reference value.
ses and PASS will be displayed; if the measured value is lower
en the test fails and NG is displayed.
M, 30M, 40M, and 50M.
e test section above.
than the
.
7. DataRecording
The MG320 can store, recall, and clear up to 99 readings (01-99).
1. Press the
The displayed counter increments to the next available memory
2.
To recall a readi
3.
buttons to scroll through the stored readings. The stored reading counter keeps track of the
memory location (01-99). Press
4.
Press and hold t
button to save a displayed reading.
ng, press the
he
button for 2 seconds to erase all memory data.
button (RECALL will be displayed). Use the arrow
again to return to the normal mode.
location.
t to
ence,
2M, 3M,
99 Washington Street
Melrose, MA 02176
Phone 781-665-1400
Toll Free 1-800-517-8431
Visit us at www.TestEquipmentDepot.com
12 MG320-en-GB_v1.1 1/17
Page 13
8. Maintenance
WARNING: To avoid electric shock, disconnect the test leads from any source of voltage before removing the
back cover, the battery, or fuse covers.
WA
RNING: To avoid electric shock, do not operate your meter until the battery and fuse covers are in place and
fastened securely.
This Instrument 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 extr
shorten the life of
ANDLE THE METER GENTLY AND CAREFULLY. Dropping it can damage the el
3. H
the electronic parts and distort or
melt plastic parts.
or the case.
4. KEEP THE METER CLE
chemicals,
cleaning solvents, or detergents.
AN. Occasionally wipe the case with a damp cloth. DO NO
5. USE ONLY FRESH BATTERIES OF THE RECOMMENDED SIZE AND TYPE. Re
w
eak batteries so they do not leak and damage th
6. IF THE ME
removed to pr
TER IS TO BE STORED FOR A LONG PERIOD OF TIME, the batteries
event damage to th
e unit.
e unit.
8.1 BATTERY INSTALLATION
WARNING: To avoid electric shock, disconnect the test leads from any source of voltage before removing the
battery cover.
1. Turn power off and disconnect the test leads from the meter.
2. Open the rear battery cover by removing three screws using a Philli
screwdriver.
Insert the six (6) 1.5V AA batteries into battery holder, observing th
3.
correct polarit
y.
4. Put the battery cover back in place. Secure with the screws.
ps
e
emes can
ectronic parts
T use
move old or
should be
You, as the end user, are legally bound (EU Battery ordinance) to return all used batteries, 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
WARNING: To avoid electric shock, do not operate meter until the battery cover is in place and fastened securely.
8.2 REPLACING THE FUSE
WARNING: To avoid electric shock, disconnect the test leads from any source of voltage before removing the
meter cover.
1. Disconnect the test leads from the meter.
To replace the 500mA/600V fuse, remove the battery cover (three Phillips screws); the fuse w
2.
be visible to the right of the batte
Gently remove the old fuse and install the new fuse into the holder.
3.
Always use a fuse of the proper size and value (500mA/600V fast blow).
4.
5.
Replace and secure the rear battery cover.
WARNING: To avoid electric shock, do not operate meter until the fuse cover is in place and fastened securely.
ries (recessed).
13 MG320-en-GB_v1.1 1/17
ill
Page 14
9. Specifications
Function RangeResolutionAccuracy
DC Voltage 600V 0.1V(2.0% reading + 3 digits)
AC Voltage 600V 0.1V(2.0% reading + 3 digits)
Specified from 5% of range to 100% of range
Input impedance: 10M
Min. Measured Voltage: 0.1V
Frequency 50~400Hz
Input protection: 600V DC and AC rms
Low Resistance
& Continuity
Insulation Resistance Measurements
50V test voltage 0.01M~19.99M
100V test voltage 0.01M~19.99M
250V test voltage 0.01M~19.99M
500V test voltage 0.01M~19.99M
1000V test
voltage
Short-circuit current < 2mA
Insulation Resistance Alerts
50V: 0.01M~50.0M (alert buzzer sounds when resistance is <1M)
100V: 0.01M~100.0M (alert buzzer sounds when resistance is <1M)
250V: 0.01M~200.0M (alert buzzer sounds when resistance is <4M)
500V: 0.01M~500M (alert buzzer sounds when resistance is <4M)
1000V: 0.01M~10.0G (alert buzzer sounds when resistance is <4M)
Note: Accuracy is stated at 23oC (75oF) and 45~75% RH.
Note: Calibration interval: 1-year maximum
Note: Temperature coefficient: 0.1 x stated accuracy/C
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.
General Specifications
Display 5999 count, backlit, LCD with bargraph
Ranging Automatic
Storage capacity 99 records (01-99)
Input Impedance >10MΩ
AC Response True rms
ACV Bandwidth 50Hz to 400Hz
Over range indication “>” is displayed
Auto Power Off After 3 minutes of inactivity
Polarity Automatic (no indication for positive); Minus (-) sign for negative
Measurement Rate 2 times per second, nominal
Low Battery Indication “
Battery Six (6) 1.5V ‘AA’ batteries
Consumption 500mA (at a 1000V test voltage); 10mA in nominal conditions
Fuse 500mA/600V fast blow
Enclosure Double molded, IP 40
Operating Temperature 0ºC~40ºC (32ºF~104ºF)
Storage Temperature -20
Operating Humidity <85%
Storage Humidity <90%
Operating Altitude 2000m (7000ft.) maximum
Weight 0.7kg (1.5 lbs.) with batteries
Size 225[L] x 103[W] x 59[D] mm (8.8[L] x 4.1[W] x 2.3[D] in.)
Safety This instrument is designed in strict compliance with safety standard
” is displayed if battery drops below operating voltage
o
C~60oC (-4oF~140oF)
IEC61010, overvoltage standard (CAT IV 600V) and pollution degree II.