Extech MG320 Instruction Manual

Insulation Tester + DMM

Model MG320

USER MANUAL

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

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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

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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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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. MeterDescription

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

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