Marmonix 30-2 Insulation Resistance Tester (2500 V Digital Megohmmeter)

The Marmonix 30-2 insulation resistance tester is a battery-powered digital megohmmeter with three test voltages, 500 V, 1000 V and 2500 V, and a range up to 20 GΩ at ±(3%+5). Before a test it can confirm a circuit is dead by reading AC voltage up to 600 V. Other functions are auto range, data hold, a low-resistance buzzer and a low-battery warning, shown on a 1999-count LCD. Six AA cells power the 680 g unit. Compare voltages in the Marmonix insulation testers range (the MIR-510 goes to 5 kV), or follow the step-by-step insulation resistance test guide.

Marmonix 30-2 Digital Megohmmeter Insulation Tester checks insulation resistance during electrical maintenance. The digital megohmmeter helps technicians look for deterioration, moisture, contamination, or other conditions that can reduce separation between conductors and equipment surfaces. A clear test record supports preventive maintenance and troubleshooting when the correct procedure is used.

Use the 30-2 only on de-energized equipment. Follow site safety procedures, test limits, discharge requirements, and the product instructions. Verify that a motor, cable, panel, or other asset is isolated before connecting the tester. Record the asset identifier, test configuration, environmental conditions, and result so readings can be compared over time.

For example, a maintenance crew can use the 30-2 to check a motor cable during a planned shutdown before returning equipment to service.

The 30-2 supports routine checks on motors, cables, and electrical systems, but it does not replace a complete diagnostic assessment or electrical safety program. Compare readings with manufacturer guidance and site acceptance criteria. Investigate unexpected changes before energizing the asset. Keep leads and terminals clean, inspect accessories, and allow equipment to discharge after testing.

Browse related products in our insulation testers category. Select an instrument that matches the voltage, environment, and documentation needs of the work. Store accessories safely, label test leads, and include asset history in the maintenance record. Consistent procedures make results more useful for planning, reporting, and handover between technicians across scheduled service work. Review trends after each service visit, note unusual readings, and keep the instrument with its accessories in a protected, dry location.

30-2 technical specifications

Figures from the 30-2 datasheet:

Case study: picking the test voltage and reading the result on a motor

A pump motor has tripped after a wet week, and the maintenance lead wants an insulation check before it runs again. The motor is locked out, its supply is proved dead, and the cable is disconnected at the terminal box.

IEEE 43, the usual reference for rotating machines, links the DC test voltage to the winding rating:

For this 400 V motor the 500 V range applies. The one-minute value is compared with the IEEE 43 minimum, 5 MΩ for random-wound and low-voltage form-wound machines and 100 MΩ for most form-wound windings, and with the motor’s own history. A reading that has dropped well below the last dry-weather result points to moisture, so the motor is dried and retested before restart.

Marmonix 30-2 megohmmeter: quick answers

What test voltages does the 30-2 have?

Three DC test levels: 500 V, 1000 V and 2500 V, so one unit covers low-voltage motors, cables and machines rated up to 5 kV.

What is the highest insulation reading on the 30-2?

It reads up to 20 GΩ; the stated accuracy over the whole insulation range is ±(3%+5).

Can the 30-2 check that a circuit is dead before testing?

Yes. It reads AC voltage up to 600 V at ±(2%+5), so you can confirm isolation before applying a test voltage.