Promotions
The Problem: Low-Current Testing Doesn’t Tell the Whole Story
A circuit breaker contact can look perfect on a standard milliohm test and still fail under load. That’s because contact resistance readings taken at 1 A or 10 A don’t reveal how a joint behaves when it’s actually carrying fault current or heavy switching loads. Loose bolted busbar connections, pitted breaker contacts, and degraded welded joints often pass a low-current check and then run hot — or fail outright — the moment real current flows through them.
For electrical contractors, substation maintenance crews, and industrial reliability teams working across Australia’s electricity network, this gap between “tests fine” and “performs fine” is a genuine risk. A missed high-resistance joint in a switchboard or substation bus can mean nuisance tripping, localised heating, insulation degradation, or in the worst case, a thermal event during a planned outage window when there’s no time to re-test and re-terminate. Standard multimeters and clamp meters simply aren’t built to inject the current levels needed to properly qualify these connections, and general-purpose micro-ohmmeters rated for a few amps won’t replicate real-world switching or fault conditions either.
The Solution: High-Current Testing in a Compact, Field-Ready Package
The Megger DLRO600 addresses this directly by pushing test current up to 600 A DC — a level that genuinely exercises high-current joints the way they’re meant to be exercised, rather than just sampling them at a token current. It measures resistance from 0.1 µΩ up to roughly 1 Ω, using a four-terminal (Kelvin) technique that separates the current-carrying leads from the voltage-sensing leads. This cancels out test lead and contact resistance from the measurement, so what’s on the display is the actual resistance of the joint under test — not an artefact of how far the leads run or how hard the clamps are gripping.
What makes the DLRO600 genuinely practical on-site is the balance Megger has struck between output power and portability. It weighs less than 14.5 kg and measures roughly 410 x 250 x 270 mm, which is remarkably compact for an instrument capable of sustaining 600 A for over 60 seconds continuously at 20°C ambient. That’s enough grunt to properly test large busbar joints and circuit breaker contacts without the instrument becoming the bottleneck in your test sequence, and it’s light enough that one technician can carry it into a switchroom or up to a substation bay without a trolley.
Three test modes cover the range of jobs contractors actually face. Auto mode is built for repetitive testing — connect the current leads to a busbar run once, then simply touch the potential leads across each joint in turn; the DLRO600 detects the connection, fires a test automatically, and stops, which speeds up multi-joint busbar surveys considerably. Normal mode runs a single 7-second test cycle for one-off contact checks. Continuous mode holds current flowing and refreshes the reading every 2 seconds, useful for monitoring a joint’s behaviour as it’s flexed, torqued, or thermally cycled during commissioning work.
Built for the Way Australian Trade Professionals Actually Work
Every result — up to 300 of them — can be tagged with a note via the on-board alphanumeric keypad and stored in battery-backed memory that retains data for up to 10 years, which matters when you’re compiling a compliance report weeks after the site visit and need to remember which reading came from which panel. Results transfer via RS232, either in real time to a printer or in batch to a PC running Megger’s Download Manager software, so field data becomes a proper test report without manual transcription.
The DLRO600’s power supply tolerates 207–265 V at 50/60 Hz for full-rated output, which sits comfortably within Australia’s 230 V nominal single-phase supply and its normal tolerance band — no step-up transformer or special site power needed for standard mains circuits. Reduced output is still available down to 100 V, useful where site power is constrained. The instrument carries IEC61010-1 safety and IEC61326-1 EMC compliance, the baseline international standards that AS/NZS 61010.1 and AS/NZS 61326.1 are aligned with for Australian electrical test equipment.
Where the DLRO600 Earns Its Keep
Circuit breaker maintenance: Contact resistance testing on MV and HV breakers during scheduled outages, where a rising resistance trend across maintenance cycles flags contact wear before it causes a problem.
Switchgear and busbar work: Testing bolted and welded busbar joints in switchboards, switchrooms, and substations — Auto mode makes multi-joint surveys along a busbar run considerably faster than manual point-and-test methods.
Industrial and mining maintenance: Verifying weld and connection integrity on heavy plant, conveyor bonding, and high-current distribution equipment where contact degradation leads to localised heating and downtime.
Rail and transit: Checking rail bonding and catenary connection integrity, where high-current contact quality is directly tied to service reliability.
Calibration and test labs: As a reference-grade low-resistance source for verifying other low-resistance test equipment, backed by the DLRO600’s own accuracy specification of better than 1% across its mid-range.
Why Buy It Here
We stock genuine Megger test and measurement equipment backed by local technical support that understands Australian compliance requirements and site conditions — not just a spec sheet. If you need calibration traceability, loan units, or help specifying the right lead set for your longest busbar run, our team can talk you through it before you buy, not just after.
Technical Specifications
| Specification | Value | Why It Matters |
|---|---|---|
| Test current range | 10 A to 600 A DC (unsmoothed), 1 A steps | Genuinely exercises high-current joints instead of sampling at token current levels |
| Current accuracy | ±2% ± 2 A | Confirms the actual test current delivered, important for repeatable trend data |
| Resistance range | 0.1 µΩ to 999.9 mΩ (approx. 1 Ω) | Covers everything from pristine low-resistance joints to degraded high-resistance faults |
| Best resolution | 0.1 µΩ | Detects fine changes in contact resistance over successive maintenance cycles |
| Resistance accuracy | Better than 1% from 100 µΩ to 100 mΩ | Reliable enough for calibration-grade trend and compliance reporting |
| Voltage accuracy | ±0.5% ± 0.1 mV | Underpins the four-terminal measurement’s overall precision |
| Measurement technique | Four-terminal (Kelvin) | Cancels test lead and contact resistance so the reading reflects the joint, not the setup |
| Maximum continuous test time | >60 seconds at 600 A, 20°C ambient | Enough dwell time to properly stress large busbar and breaker joints |
| Test modes | Manual/Normal, Auto, Continuous | Auto speeds up multi-joint busbar surveys; Continuous supports monitoring during mechanical or thermal work |
| Test time (Normal/Auto) | 7 seconds per cycle | Fast enough to keep multi-point survey work moving on an outage-limited schedule |
| On-board memory | 300 result sets with notes, battery-backed for 10 years | Field data survives long report-writing delays without a laptop on site |
| Memo field | 200 characters | Enough room to record joint ID, location, or condition notes against each result |
| Data output | RS232, real-time or batch via Download Manager software | Converts field readings into a proper test report without manual transcription |
| Power supply | 207–265 V, 50/60 Hz for full output; reduced output to 100 V | Sits comfortably within Australia’s 230 V nominal supply tolerance, no step-up gear needed |
| Operating temperature | -10°C to +50°C | Suits Australian field conditions from cool-climate substations to outdoor summer work |
| Storage temperature | -25°C to +65°C | Tolerates ute toolbox and warehouse storage extremes |
| Humidity | Up to 95% RH, non-condensing | Copes with humid coastal and tropical northern Australia site conditions |
| Altitude | Up to 2000 m | Covers virtually all Australian test locations including alpine sites |
| Dimensions | 410 x 250 x 270 mm | Compact enough for one-person transport into switchrooms and substation bays |
| Weight | 14.5 kg (excluding test leads) | Under 15 kg keeps it genuinely field-portable for a 600 A instrument |
| Safety standard | IEC61010-1 | International base standard aligned with AS/NZS 61010.1 for Australian test equipment safety |
| EMC standard | IEC61326-1 | International base standard aligned with AS/NZS 61326.1 |
| Included accessories | 5 m test lead set, RS232 download cable, Download Manager software, quick start guide | Ready to test out of the box without sourcing separate leads |
Note: The manufacturer datasheet references IEC standards directly. See Publisher Notes below regarding AS/NZS equivalence and RCM status.
What is the Megger DLRO600 used for? The Megger DLRO600 is a 600 A micro-ohmmeter used to measure very low resistance — from 0.1 µΩ up to around 1 Ω — on high-current electrical joints such as circuit breaker contacts, busbar connections, switch contacts, and welded joints. It’s built for maintenance and commissioning work where a low-current test wouldn’t properly stress the joint under test.
How much test current does the DLRO600 output? The DLRO600 delivers test currents from 10 A up to 600 A DC in 1 A steps, subject to load resistance and supply voltage. It can sustain 600 A continuously for more than 60 seconds at 20°C ambient, which is enough to properly test large busbar joints and breaker contacts.
How does the DLRO600 measure resistance so accurately? It uses a four-terminal (Kelvin) measurement technique, which separates the current-carrying leads from the voltage-sensing leads. This cancels the resistance of the test leads and connections from the reading, leaving a measurement of just the joint or contact under test — accurate to better than 1% across its mid-range (100 µΩ to 100 mΩ).
Is the Megger DLRO600 suitable for Australian 230 V mains supply? Yes. The DLRO600’s power supply operates at full rated output from 207 V to 265 V at 50/60 Hz, which comfortably covers Australia’s 230 V nominal single-phase supply and its standard tolerance range without needing a step-up transformer.
How many test results can the DLRO600 store? The DLRO600 stores up to 300 test results with notes in on-board memory, battery-backed to retain data for up to 10 years. Results can be downloaded in real time or in batch via the RS232 port using Megger’s Download Manager software.
What’s the difference between Auto, Normal, and Continuous mode on the DLRO600? Normal mode runs a single 7-second test cycle for one-off checks. Auto mode automatically detects when potential leads make contact and fires a test, which speeds up sequential busbar or multi-joint surveys. Continuous mode holds current flowing and refreshes the reading every 2 seconds, useful for monitoring a connection while it’s being worked on.
How heavy and portable is the DLRO600? The DLRO600 weighs 14.5 kg excluding test leads and measures 410 x 250 x 270 mm, making it compact enough for one technician to carry into a switchroom or substation bay despite its 600 A output capability.
