Megger MOM600A Micro Ohmmeter

The Megger MOM600A is a professional-grade 600 A micro ohmmeter engineered for precise and reliable measurement of very low resistance values in critical electrical connections. Designed to withstand the demands of industrial environments, this instrument is ideal for electrical maintenance technicians, test engineers, and reliability specialists who need to verify the integrity of high-current joints and contact interfaces to prevent failures. Its robust construction and high current capability make it suitable for field service as well as shop-floor testing in substations, power plants, and manufacturing facilities.

At its core, the MOM600A can generate a DC output current up to 600 A, allowing it to fully excite high-current paths and accurately measure resistance down to the micro-ohm range. This high-current output ensures that even minor resistive anomalies—which can lead to overheating and equipment failure—are detected during routine maintenance or commissioning tests. Typical applications include measuring contact resistances in high-voltage circuit breakers, disconnecting switches, knife-contact fuses, bus bar joints, line joints, and other high-current connections where minimal resistance is critical.

The measurement range of the MOM600A typically extends from 0 to 1,999 µΩ with a resolution of 1 µΩ, and its accuracy is approximately ±1 % of reading plus 1 digit when using test currents from 100 A to 600 A. To ensure precise results, the instrument uses a four-terminal (Kelvin) connection technique, separating the current-carrying cables from the voltage-sensing leads to minimize errors caused by lead resistance—a crucial factor in achieving reliable low-resistance measurements in real-world field conditions.

One of the MOM600A key advantages is its rugged, portable design. The unit comes with highly flexible heavy-duty current cables and separate sensing leads, all stored in a sturdy transport case that protects the instrument and its accessories during transit or harsh field use. Built to operate reliably in extreme temperature ranges—from arctic cold to tropical heat—the MOM600A maintains accuracy and performance in diverse climates, making it a dependable choice for utilities, industrial maintenance teams, and service contractors.

The instrument is mains powered, with industrial-grade protection features including miniature circuit breakers and thermal cutouts. Depending on the supply version, it delivers the required current with an appropriate open-circuit voltage and supports remote shunt measurement or integration with external instrumentation. These design features combine safety and performance, allowing professionals to perform repeatable, high-current resistance measurements without risk to the equipment.

In practical applications, the MOM600A supports preventive maintenance programs by identifying increases in contact resistance that often precede overheating, arcing, or unexpected outages. By incorporating repeatable low-resistance testing into routine inspections, maintenance crews can detect early signs of connection degradation, plan proactive replacements or adjustments, and enhance system reliability. Its intuitive operation and high measurement fidelity make it ideal for commissioning tests, periodic maintenance checks, and troubleshooting during fault investigations.

Technical Specifications

General / Physical

Model: MOM600A Micro‑Ohmmeter
Instrument Type: Low-resistance measurement for high-current connections
Design: Compact, rugged, industrial/field-ready
Power Supply: Mains AC 115 V / 230 V, 50 / 60 Hz
Maximum Power Consumption: ~4370 VA (115 V) / ~7360 VA (230 V)

Measurement Section

DC Output Current: 0 – 600 A DC
Resistance Range: 0 – 1,999 µΩ
Resolution: 1 µΩ
Accuracy: ±1 % of reading + 1 digit (at 100 A – 600 A test current)
Measurement Method: Four-terminal (Kelvin) connection with separate current and sensing leads to minimize lead resistance error

Voltage & Shunt Output

Open-Circuit Voltage:
• ±5.2 V DC (115 V model)
• ±9 V DC (230 V model)
Current Shunt Output: 10 mV / 100 A ±0.5 %, maximum 60 mV, maximum 10 V relative to ground

Load Capability (230 V Model)

Output Current	Minimum Voltage	Maximum Load Time	Rest Time	Input Current
100 A DC	8.3 V DC	–	–	6 A
300 A DC	7.2 V DC	2.5 min	15 min	16 A
600 A DC	5.6 V DC	15 s	5 min	32 A

Operating Environment

Operating Temperature:
• 0 °C – +50 °C (115 V)
• 0 °C – +40 °C (230 V)
Storage / Transport Temperature: -40 °C – +70 °C
Relative Humidity: 5 % – 95 % non‑condensing

Dimensions & Weight

Unit Dimensions: ~356 × 203 × 241 mm
Transport Case Dimensions: ~610 × 290 × 360 mm
Weight: ~16.8 kg including standard cables (varies depending on accessories)

Accessories & Included Items

Typically supplied with heavy-duty current cables and separate sensing leads in a rugged transport case

Summary of Function

The Megger MOM600A is a high-current (up to 600 A DC) micro-ohmmeter for measuring extremely low contact resistance in high-current connections such as busbar joints, circuit breakers, isolators, and main cable connections. It is designed for preventive maintenance, commissioning, and field testing in industrial and substation environments, providing accurate measurements that help prevent overheating and early equipment failures.

Megger MOM600A

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