Extech Instruments MG320-NIST User manual

EXCH®
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Insulation Tester+ DMM
Model MG320
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USER MANUAL
Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
TestEquipmentDepot.com

2 MG320-en-GB_v1.1 1/17
TableofContents
1. INTRODUCTION 3
2. SAFETY 3
3. METERDESCRIPTION 5
4. CONTROLBUTTONS 6
5. SYMBOLSANDANNUNCIATORS 6
6. OPERATINGINSTRUCTIONS 7
6.1DisplayBacklight 7
6.2DataHold 7
6.3LowBatteryIndication 7
6.4DCVOLTAGEMEASUREMENTS 7
6.5ACVOLTAGEMEASUREMENTS 8
6.6LOWRESISTANCE/CONTINUITYMEASUREMENTS 9
6.7INSULATIONRESISTANCEMEASUREMENTS 10
6.7.1DisableInsulationTestLockMode 10
6.7.2InsulationResistanceTestTimeSetup 11
6.7.3DielectricAbsorptionRatio[DAR]InsulationTesting 11
6.7.4PolarizationIndex[PI]InsulationTesting 11
6.7.5ComparatorUtility 12
7. DATARECORDING 12
8. MAINTENANCE 13
8.1BATTERYINSTALLATION 13
8.2REPLACINGTHEFUSE 13
9. SPECIFICATIONS 14

3 MG320-en-GB_v1.1 1/17
1. Introduction
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 20G
Low Resistance/Continuity Measurements to 20k
Auto Ranging measurements
Polarization Index (PI) and Dielectric Aborption Ratio (DAR) tests
Five (5) Insulation Resistance test voltages (50, 100, 250, 500, and 1000V)
Insulation Resistance tests in10% voltage steps (from 50% to 120% of range)
Front panel LED test voltage alert lamp
Eight (8) Insulation Resistance measurement ranges (automatic ranging)
Pass/Fail Comparator function
Auto-discharge at end of test
High voltage display symbols
Hand’s free test lock feature
Manually store and recall up to 99 readings
Overload indication
Optional remote test probe for controlling the TEST button remotely
Test leads, alligator clips, batteries, user manual, and case included
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

4 MG320-en-GB_v1.1 1/17
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.
1. NEVER apply voltage to the meter that exceeds the specified maximum:
Input Protection Limits
Function Maximum Input
V DC or V AC 600VDC/AC rms
Resistance/Continuity 500mA/600V fuse protected input
Insulation Resistance 250VDC/AC rms
Surge Protection: 8kV peak per IEC 61010
2. USE EXTREME CAUTION when working with high voltages.
3. DO NOT measure voltage if the voltage on the "COM" input jack exceeds 600V above earth
ground.
4. NEVER connect the meter leads across a voltage source while the function switch is in the
resistance mode. Doing so can damage the meter.
5. ALWAYS discharge filter capacitors in power supplies and disconnect the power when making
resistance tests.
6. ALWAYS turn off the power and disconnect the test leads before opening the covers to replace
the fuse or batteries.
7. NEVER operate the meter unless the battery/fuse cover is 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.

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Test Equipment Depot - 800.517.8431 - 99 Washington Street Melrose, MA 02176
TestEquipmentDepot.com