Can your multimeter and insulation resistance tester do this?

24 March 2022


Insulation resistance testers and digital multimeters that measure voltage and current are two of the most relied-upon tools for solar project commissioning and periodic maintenance testing. When it comes to quality control and system safety, both tools are indispensable.

All it takes is a small cut in a piece of solar wire insulation. Left unnoticed, the damage can cause a ground fault once the inverters are commissioned, presenting electrical shock and fire hazards.

Measuring voltage and current, you can verify that systems are safe to energize at commissioning. You can also identify maintenance issues as they arise and compare modeled performance with actual performance.

Megger’s MIT2500 insulation resistance tester and DCM1500S multimeter give solar technicians a pair of workhorse tools for the greatest ease of use, precision, and reliability.

Insulation resistance testing up to 2500 V

The MIT2500 is a convenient megohmmeter that fits in the palm of your hand. It’s the smallest 2.5 kV tester on the market.

While the tool measures voltage, resistance, and continuity, its primary function is to detect when a system’s electrical wire insulation has been compromised.

The MIT2500 stands out for its extraordinary range from 50 V to 2500 V with readings up to 200 GΩ. Use the tool to test circuits on both the ac and dc sides of the PV system. Easily adjust voltage output to match the segment of the circuit you are testing.

Maintain consistency as you test all your source circuit strings. With preset time features, you can be sure readings are precise.

Many contractors are adopting the international standard IEC62446 and supplemental guides such as SunSpec Alliance’s “Commissioning for PV Performance” for documentation required before customer handoff. IEC62446 calls for insulation resistance testing as part of the safety and commissioning protocol.

The MIT2500 is the only handheld IR tester that includes a guard terminal that helps avoid inaccurate diagnostic results from surface leakage currents. Connect the guard terminal to a bare wire wrapped around the surface of the object under test.

It also comes with a redesigned carrying case for better protection in the field and a magnetic strap for easy positioning while testing your system.

After testing, easily upload results to a computer using the MIT2500’s Bluetooth and pairing capabilities.

One tool for all voltage, current measurements

The newest instrument in Megger’s suite of solar testing tools, the DCM1500S is the only multimeter needed for solar applications. It can test voltages up to 2,000 Vdc, true RMS up to 1,500 Vac, and amperages up to 1,500 A on the ac and DC sides of the system.

The DCM1500S comes with a test lead set, test probes, crocodile clips, a TP100 temperature probe, a PVHV1 lead set, a PVHV2 lead set (with integrated MC4 plugs), a manual, a carrying case, and batteries.

Use the standard test leads to measure ac and dc voltages of less than 1,000 V and Megger PVHV test leads for voltages greater than 1,000 V.

Measuring current with the clamp meter is one of the instrument’s more powerful features. The default setting is for DC amperage. Turn the rotary switch to the “A” setting to initiate current reading.

Another useful feature is integrated temperature measurement. Attach the TP100 temperature probe to a solar module to record the operating temperature.

Data logging is a real time saver in the field. Collect data automatically at predetermined time intervals or manually. Store up to 4,000 measurements in the on-board memory. Then upload data with a Bluetooth connection using Megger Link, an app for iOS and Android devices. You can also download data or connect directly to the instrument to see current measurements in a graph.

Additional features include inrush current and frequency measurements, resistance, continuity, min/max measurements, volt seek, an automatic flashlight, and a no-touch voltage sensor.

Get a full picture of your solar projects

By taking routine measurements and keeping good records of the results, you can keep close tabs on the condition and performance of your solar projects over time.

Find all the tools necessary for the job, including the MIT2500 and DCM1500S, in Megger’s Solar Testing Kit.

This post completes a three-part series we put together for contractors attending the NABCEP 2022 Continuing Education Conference, March 28-31. Visit the Megger blog for previous posts on reasons it might be time to upgrade your solar testing toolkit and how Megger has developed innovative solutions for solar technicians.

If you are attending NABCEP 2022, don’t forget to visit us at Booth #2. See you in Phoenix!