The Extech MG320 is a CAT IV-rated combination insulation resistance tester and True RMS digital multimeter, two critical diagnostic instruments in a single, professional-grade handheld package. With selectable test voltages from 50V to 1000V, insulation resistance measurement to 20GΩ, and a 6000-count backlit LCD with analog bar graph, the MG320 delivers comprehensive insulation integrity testing alongside full True RMS multimeter functionality for aircraft wiring system diagnostics, MRO maintenance, and electrical infrastructure testing. PI/DAR mode, programmable timer, comparator function, and 99-reading memory add advanced testing capability for thorough insulation condition assessment and maintenance documentation.
Key Features
- Insulation test voltages: selectable 50V, 100V, 250V, 500V, and 1000V for testing aircraft wiring, motors, and insulation systems at appropriate test levels
- Insulation resistance range to 20GΩ for detecting degraded insulation in aircraft wiring harnesses, motors, and electrical systems
- PI (Polarization Index) and DAR (Dielectric Absorption Ratio) modes for detailed insulation condition analysis beyond simple resistance measurement
- Programmable timer for consistent, standardized insulation test durations across maintenance teams
- Comparator function for pass/fail testing against user-defined resistance thresholds
- 99-reading memory for on-site documentation of insulation test results
- 6000-count backlit LCD with analog bar graph for trend visualization during testing
- Full True RMS multimeter functions: AC/DC voltage to 600V, resistance, and continuity
- CAT IV-600V safety rating for use on primary electrical distribution systems
Specifications
- Insulation Test Voltages: 50V, 100V, 250V, 500V, 1000V
- Insulation Resistance Range: 50MΩ / 100MΩ / 200MΩ / 500MΩ / 2GΩ / 10GΩ / 20GΩ
- AC Voltage (True RMS): up to 600V
- DC Voltage: up to 600V
- PI Mode: Yes (Polarization Index)
- DAR Mode: Yes (Dielectric Absorption Ratio)
- Programmable Timer: Yes
- Comparator: Yes (user-defined threshold)
- Memory: 99 readings (store and recall)
- Display: 6000-count backlit LCD with analog bar graph
- True RMS: Yes
- Safety Rating: CAT IV-600V
- Power: Rechargeable battery or AC adapter
Applications
The MG320 is an essential instrument for aviation maintenance technicians and MRO electricians who perform insulation resistance testing on aircraft wiring harnesses, motors, generators, and electrical distribution systems as part of scheduled maintenance, post-repair verification, and airworthiness inspections. PI and DAR testing modes enable advanced insulation condition assessment for aircraft motors and generators, detecting insulation aging and moisture absorption beyond what a simple resistance measurement reveals. The MG320's CAT IV-600V rating supports safe use on aircraft primary electrical systems and external power connections, while the memory and programmable timer features support systematic, documented insulation testing programs for FAA compliance and MRO maintenance records.
Need Your Extech MG320 Calibrated?
- PJi operates an ISO/IEC 17025 Accredited Calibration Lab and provides NIST-traceable calibration for the Extech MG320 at purchase.
- Documentation satisfies FAA Part 145, ISO 9001, and AS9100 requirements.
- PJi is the one-stop source: instrument and certificate in one transaction.
Why Buy from Pilot John International?
- Pilot John International is an authorized Extech distributor with an in-house ISO/IEC 17025 Accredited Calibration Lab.
- One-stop source for Extech instruments and NIST-traceable calibration in a single transaction.
- We serve aviation maintenance, FAA Part 145 repair stations, and industrial MRO facilities.
- Full-catalog availability and same-business-day shipping on in-stock items.
| General Information | |
|---|---|
| Part # | MG320 |
| Manufacturer | Extech Instruments |
| Specifications | |
|---|---|
| AC Voltage Range | up to 600V (True RMS) |
| Autoranging | Yes |
| Comparator | Yes (user-defined threshold) |
| DAR Mode | Yes (Dielectric Absorption Ratio) |
| DC Voltage Range | up to 600V |
| Display | 6000-Count Backlit LCD with Analog Bar Graph |
| Insulation Resistance Range | 50MΩ to 20GΩ |
| Insulation Test Voltages | 50V, 100V, 250V, 500V, 1000V |
| Memory | 99 readings (store and recall) |
| PI Mode | Yes (Polarization Index) |
| Programmable Timer | Yes |
| Safety Rating | CAT IV-600V |
| True RMS | Yes |
AIRCRAFT COMPATIBILITY
| Compatible Aircraft* |
|---|
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QUESTIONS & ANSWERS
The Extech MG320 is used to evaluate the condition of electrical insulation while also performing standard multimeter functions such as AC/DC voltage, resistance, and continuity testing. In aviation maintenance environments, it can help technicians identify insulation degradation, moisture intrusion, wiring faults, and potential electrical failures before they become safety concerns. Because it combines insulation testing and multimeter functionality in a single instrument, it streamlines troubleshooting and preventive maintenance activities.
For many maintenance applications, yes. The MG320 performs insulation resistance testing up to 20GΩ with selectable test voltages up to 1000V, providing the core functionality of a dedicated megohmmeter while also incorporating True RMS multimeter capabilities. This combination reduces the need to carry multiple test instruments and allows technicians to perform both insulation testing and electrical troubleshooting with a single device.
Different electrical systems and components require different test voltages to properly evaluate insulation integrity without risking unnecessary stress on sensitive equipment. The MG320 offers five selectable test voltages – 50V, 100V, 250V, 500V, and 1,000V – allowing technicians to match the test to the specific aircraft wiring, motor, generator, or electrical component being evaluated. This flexibility supports more accurate and application-specific insulation testing.
The MG320 measures insulation resistance up to 20GΩ, allowing technicians to detect gradual insulation deterioration long before a complete failure occurs. Small reductions in insulation resistance can indicate contamination, aging, moisture intrusion, or thermal damage within wiring systems and electrical equipment. Early detection helps maintenance teams address issues proactively, reducing the risk of unexpected aircraft downtime.
The MG320 allows insulation testing in 10% voltage increments from approximately 50% to 120% of the selected test range. This feature enables technicians to observe how insulation responds under increasing electrical stress, which can reveal weaknesses that may not be apparent during a single-voltage test. Step voltage testing is particularly useful for evaluating aging insulation systems and detecting hidden deterioration.
The comparator mode allows users to establish predefined resistance thresholds and receive immediate pass/fail indications during testing. This can help standardize inspection procedures across maintenance teams and reduce the time required to evaluate results manually. For organizations performing repetitive inspections, the comparator function helps improve consistency and documentation efficiency.
Yes. The MG320 automatically discharges stored test voltage after an insulation resistance test is completed. This safety feature helps protect technicians and equipment by reducing the risk of exposure to residual charge remaining on the circuit under test. Automatic discharge also allows maintenance personnel to move more quickly between testing tasks.
Yes. The meter includes a test lock function that allows insulation resistance tests to continue without requiring the technician to hold the test button throughout the procedure. This is especially useful during extended PI and DAR testing sequences or when working in challenging maintenance environments. The hands-free capability can improve both convenience and productivity during routine inspections.
The MG320 can manually store and recall up to 99 test readings, making it easier to document inspection results and compare measurements over time. This feature supports trending analysis, preventive maintenance programs, and maintenance recordkeeping requirements. By retaining readings in the field, technicians can reduce reliance on handwritten notes and improve data accuracy.
Yes. PJi operates an ISO/IEC 17025-accredited calibration laboratory and can provide NIST-traceable calibration for the Extech MG320 at the time of purchase. This service helps support quality management and compliance requirements for FAA Part 145 repair stations, AS9100-certified organizations, and other aviation maintenance operations. Purchasing the instrument and calibration together simplifies procurement while helping ensure measurement confidence and traceability.
