Marmonix MIR-505 (MIR505 / MIR 505) 5 kV High Voltage Insulation Resistance Tester

The Marmonix MIR-505 insulation tester (also typed MIR505 or MIR 505) applies 500 V, 1000 V, 2500 V or 5000 V DC to measure insulation resistance from 0.005 MΩ up to 6 GΩ on the two lower voltages and up to 60 GΩ on 2.5 kV and 5 kV. It times tests from 1 to 15 minutes, works out the polarization index (PI) and dielectric absorption ratio (DAR) with a pass/fail flag, has a guard terminal to remove surface leakage on cables, and discharges the tested item automatically when the test ends. A live-circuit warning blocks the test above 30 V. The same instrument reads AC and DC voltage from 0.5 to 600 V and low resistance from 0.12 Ω to 6 kΩ with at least 200 mA of test current, all on a 6000-count display with a bargraph. Compare the Marmonix insulation testers, or follow the step-by-step insulation resistance test guide.

High Voltage Insulation Tester MIR-505

The high voltage insulation resistance tester MIR-505 is a handheld instrument designed primarily to make AC/DC voltage, resistance, and Continuity test / insulation resistance measurement.

High Voltage Insulation Tester MIR-505 Features

Functions listed for the MIR-505:

• Wide range measurements from 500V to 5000V and up to 60GΩ.
• Large 6000 count digital display with bargraph and backlight.
• Polarization index measurement (PI).
• Auto ranging & Timer measurement function.
• Indication of output voltage and discharge voltage.
• Auto-discharge function and voltage output warning function.
• Auto power off and battery check.
• MAX/MIN, PEAK, Relative value & Data hold functions for DC/AC voltage measurements.

High Voltage Insulation Tester MIR-505 specifications:

High Voltage Insulation Tester MIR-505 Accessories

Leads and items listed with the MIR-505:

• One plug test lead to one alligator clip (Black color)
• One plug test lead to one alligator clip (Green color)
• One plug test lead to one alligator clip (Red color)
• Two plug test lead to one alligator clip (Red color)
• Battery Carry Case
• Power Adaptor

Case study: deciding whether a damp motor winding can go back into service

A pump motor has stood idle through a wet season. A single one-minute megohm reading may look acceptable even when moisture is still in the windings, so the maintenance team wants a trend over time before switching it on.

Following the MIR-505 manual, the test runs in this order:

• Prove it dead: the motor is isolated; if more than 30 V is present, the tester shows a warning and will not start the insulation test.
• Connect for a fair reading: the earth lead goes to the motor frame and the line lead to the winding; on a cable run, the guard lead takes surface leakage out of the result.
• Run PI, not just a spot value: PI divides the 10-minute reading by the 1-minute reading, and DAR divides the 1-minute reading by the 30-second one, so a winding that is still absorbing moisture shows a low ratio.
• Let it discharge: the leads stay connected after the test until the auto-discharge has brought the voltage monitor back to 0 V.

The manual quotes IEEE 43-2000, which sets a minimum PI of 2.0 for class B, F and H insulation. A lower ratio sends the motor for drying and a retest rather than straight back into service.

MIR-505 (MIR505): buyer questions

What test voltages does the MIR-505 use?

Four DC test voltages: 500 V, 1000 V, 2500 V and 5000 V, each with an open-circuit tolerance of +20%/−0%. The 500 V and 1000 V ranges read up to 6 GΩ, and the 2500 V and 5000 V ranges up to 60 GΩ.

Does the MIR-505 measure PI and DAR?

Yes. PI is the 10-minute reading divided by the 1-minute reading, and DAR is the 1-minute reading divided by the 30-second reading; both run automatically and show pass or fail. A timer from 1 to 15 minutes is also built in.

Can the MIR-505 also check voltage and continuity?

Yes. It reads AC and DC voltage from 0.5 to 600 V (AC from 40 to 400 Hz) and low resistance from 0.12 Ω to 6 kΩ, with a continuity buzzer at 50 Ω or less and a test current of at least 200 mA.