Micro-Ohmmeter and Ductor Testing Equipment for Hire
Introduction
Megavar supplies micro-ohmmeters and ductor testers for hire across Australia, supporting contact resistance measurement on circuit breakers and switchgear, joint and connection resistance on busbars and conductors, and weld and bond integrity testing. The hire fleet covers the Megger DLRO low-resistance ohmmeter range across portable handheld units and high-current bench and field sets, from the everyday 10 A instrument through to high-current sets for the most demanding contact resistance work. The same instruments are used by Megavar commissioning engineers on substation and renewable energy projects every week.
A ductor test, the long-standing field name for a low-resistance measurement, answers one question that ordinary multimeters cannot: what is the true resistance of a current-carrying joint, contact, or connection, measured in micro-ohms. A loose or corroded busbar joint, a worn circuit breaker contact, or a poorly made cable lug presents a resistance of only tens or hundreds of micro-ohms, but at full load current that small resistance dissipates real heat, and heat is what eventually fails the connection. Measuring it reliably requires a four-terminal Kelvin measurement that eliminates the resistance of the test leads themselves, and a test current high enough to break through the surface films that would otherwise give a falsely high reading.
The Megavar micro-ohmmeter hire fleet is built on the Megger DLRO range, the established low-resistance ohmmeter family across Australian utilities and contractors. The fleet spans test currents from the portable 10 A handheld instrument, suitable for the bulk of contact and joint resistance work, up to high-current sets that drive the larger test currents some contact resistance specifications and high-current busbar joints require. Every instrument uses a four-terminal Kelvin measurement to eliminate lead resistance, and the higher-current units apply a forward and reverse current technique to cancel out standing thermal EMFs at the contact. Results store on the instrument and download for trend comparison against previous measurements on the same connection. Hire from our offices in Hobart, Launceston, Adelaide and Newcastle, with delivery Australia-wide and engineer-led support from a team that performs contact resistance testing as a regular part of substation commissioning and switchgear maintenance scopes.
Micro-ohmmeter and ductor testing applications
Circuit breaker contact resistance
Contact resistance across circuit breaker main contacts is a core commissioning and maintenance measurement. A rising contact resistance indicates contact wear, contamination, or mechanism misalignment, all of which lead to overheating under load. The measurement is taken across the closed contacts with a high test current, and compared against the manufacturer acceptance figure and against previous results on the same breaker.
Busbar, joint, and connection resistance
Bolted busbar joints, conductor connections, and cable lugs are measured to confirm the joint resistance is within specification and consistent across like joints. An outlier joint is the early warning of a connection that will overheat in service. High-current sets are used where the joint carries high current and the specification calls for a representative test current.
Weld, bond, and earth connection integrity
Low-resistance measurement confirms the integrity of welds, equipment bonds, and earth grid connections, distinguishing a sound bond from one that is mechanically tight but electrically poor. This is routine on substation steelwork, earth grid commissioning, and equipment earthing verification.
Commissioning verification on substation and renewable plant
Contact and joint resistance verification is a normal hold point in substation, solar farm, wind farm, and BESS commissioning. Megavar engineers perform these measurements as a regular part of commissioning scopes, which is why the hire fleet is maintained to commissioning standard.
When to Hire vs Buy
Hire from Megavar when...
- You need a high-current ductor set for a single commissioning or maintenance campaign
- Capital is constrained or the project rate does not justify outright purchase
- Calibration and freight on owned equipment would exceed hire cost over the project life
- You need engineer-led test set-up and result interpretation rather than the equipment alone
- You need to scale several instruments in parallel during a multi-bay switchgear commissioning
Consider purchasing when...
- Your team performs contact resistance testing on more than 60 days per year
- You have in-house engineers competent on four-terminal high-current measurement
- You can amortise the unit over its service life
- Your asset programme commits to a multi-year contact resistance trend baseline
- You require permanent on-call availability that hire cannot guarantee
Micro-Ohmmeter and Ductor Testing Equipment
Available for Hire
Megger
The DLRO 10A is a high-precision digital low resistance ohmmeter designed to measure very low resistance values with exceptional accuracy and repeatab…
The Megger DLRO 100EB is a rugged, portable 100 A digital low-resistance ohmmeter engineered for high-accuracy micro-ohm measurements in high-voltage …
The DLRO 600A is a high‑current micro‑ohmmeter engineered for measuring extremely low resistances under real high‑current conditions. With test curren…
The 300 A Handheld Micro-ohmmeter is a powerful, portable instrument designed to measure very low resistances—typically in micro-ohms—with high accura…
Calibration
All Megavar test equipment is maintained under a documented calibration programme. Instruments are calibrated either by external calibration laboratories or in-house against reference standards that are themselves laboratory-calibrated, with measurement traceable to Australian national measurement standards held by the National Measurement Institute. A current calibration certificate is available on request. If your project requires a specific calibration interval, test standard, or documentation for a client submission, tell us at enquiry on 1300 730 499 and we will confirm what applies before you commit.
Get a quote for Micro-Ohmmeter and Ductor testing equipment hire
Australia-wide delivery, current calibration, engineer-led support. Most enquiries quoted same business day.
Talk to our engineers about your project requirements.
Frequently Asked Questions
for Micro-Ohmmeter and Ductor Testing Equipment
What is ductor testing?
Ductor testing is the field name for a low-resistance measurement, taken with a micro-ohmmeter, that measures the true resistance of a current-carrying joint, contact, or connection in micro-ohms. The name comes from the original Ductor instrument, and the term is still used across the industry for any contact or joint resistance test. It is used to confirm circuit breaker contacts, busbar joints, cable connections, and bonds are sound, because a high-resistance connection overheats under load and eventually fails.
What is a micro-ohmmeter and how is it different from a multimeter?
What is contact resistance testing?
Contact resistance testing measures the resistance across a closed electrical contact, most commonly a circuit breaker main contact, using a micro-ohmmeter at a defined test current. A rising contact resistance over successive tests indicates contact wear, contamination, or mechanism misalignment. The result is compared against the manufacturer acceptance figure and against previous measurements on the same contact, which is the basis of condition-based switchgear maintenance.
Why is a four-wire (Kelvin) measurement needed?
At the micro-ohm level, the resistance of the test leads and the contact resistance where the probes touch the connection are far larger than the resistance being measured, so a two-wire measurement is meaningless. A four-wire Kelvin measurement injects current through one pair of leads and measures voltage through a separate pair, so the lead and probe-contact resistance carry no measurement current and do not affect the result. Every instrument in the Megavar fleet uses a four-terminal Kelvin measurement.
What test current do I need for contact resistance testing?
The required test current depends on the acceptance specification for the asset. Many circuit breaker and switchgear specifications call for a test current of 100 A or higher so the measurement is representative of the contact under load and breaks through any surface films, while routine joint and connection work is often satisfied by a 10 A instrument. The Megavar fleet spans 10 A, 100 A, 300 A, and 600 A so the test current can be matched to the specification. If you are unsure, our engineers can advise against the relevant standard.
What is the forward-reverse current technique?
Standing thermal EMFs at the junction of dissimilar metals in a connection can add a small DC voltage that biases a low-resistance measurement. The forward-reverse current technique takes a measurement with the current flowing one way, then again with it reversed, and averages the two, which cancels out the standing EMF and gives a true resistance. The higher-current instruments in the Megavar fleet apply this automatically.
Can a micro-ohmmeter test earth grid and bonding connections?
Yes. Low-resistance measurement confirms the integrity of welds, equipment bonds, and earth grid connections, distinguishing a connection that is mechanically tight but electrically poor from a sound one. This is routine on substation steelwork and earth grid commissioning. Note that earth grid resistance to remote earth is a separate measurement requiring an earth resistance tester, not a micro-ohmmeter; the micro-ohmmeter verifies the connections within the grid.
Do you provide test engineers as well as the equipment?
Yes. Megavar performs contact and joint resistance testing using the equipment in this rental fleet as a regular part of substation commissioning and switchgear maintenance, including test set-up, on-site execution, and result interpretation against manufacturer acceptance figures. If your project requires a turnkey survey rather than equipment hire alone, contact us with the asset type, the acceptance specification, and the test window, and we will quote a full scope.
Why Hire from Megavar
Megavar is a specialist HV testing and commissioning firm with offices in Hobart, Launceston, Adelaide and Newcastle. We perform contact and joint resistance testing as a regular part of substation commissioning and switchgear maintenance work for ElectraNet, TasNetworks, Downer, Acciona, Zinfra/Jemena, and renewable energy developers across Australia. The hire fleet exists because we built it for our own commissioning teams first, and we maintain it to the standard those teams require.
When you hire micro-ohmmeter and ductor testing equipment from Megavar you receive: full current calibration with traceable certificates, the complete current and potential lead set, a configuration tailored to your scope, and engineer-led pre-hire briefings on four-terminal connection technique and result interpretation. Our engineers can advise on the right test current for your acceptance specification, recommend the right instrument class for your scope, and help interpret the results against manufacturer acceptance figures. Where the project demands a turnkey contact resistance survey rather than equipment hire alone, we can quote on the full service. Hire periods are flexible from a single-day commissioning check through to multi-month maintenance campaigns. Delivery is Australia-wide. Call 1300 730 499 or email rentals@megavar.com.au.
Enquire about Micro-Ohmmeter and Ductor Testing Hire
Tell us about your project and we will get back to you within 24 hours with availability and a quote.
Or call us directly on 1300 730 499
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