Selected current
Use the value required by the asset procedure and verify that it lies inside the tester's published range and duty.
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Measure the closed main path in micro-ohms
Circuit Breaker Contact Resistance Test Equipment
Compare high-current micro-ohm testers for circuit breaker contacts and main conducting loops. Match the test current, resistance range, output duty, four-terminal leads, site power and reporting workflow to the approved procedure.
25 A to 200 A routes0.1 µΩ minimum resolutionPortable and AC-powered options
Kelvin connection / closed contactR = V ÷ I
48.6µΩ
I+V+V−I−
Iknown current
Vsensed drop
Rcalculated value
Control the measurement conditions
Five controls sit behind every defensible contact-resistance result
A micro-ohm number is useful only when the test setup is traceable. Define the current, lead arrangement, contact state, stabilization period and record fields before comparing results.
Four-terminal leads
Separate current injection from voltage sensing so lead resistance is not treated as contact resistance.
Closed contact state
Identify breaker, pole, phase, contact path and as-found or after-service condition on every record.
Stable reading
Apply the approved duration and observe stability without exceeding the instrument or asset test duty.
Comparable record
Keep current, connection points, temperature, date and equipment identity with the measured value.
Wrindu contact-resistance routes
Compare portable, high-output and continuous-measurement configurations
The three routes below all target micro-ohm contact or loop resistance, but their current selections, ranges, power arrangements and field workflows differ. Use the public values for shortlisting, then confirm the current datasheet and supplied accessories.
Battery-powered field route
RDHL-200HX
New Portable Loop Resistance Tester
A rechargeable field unit with six published current selections and timed output choices for portable breaker contact-resistance work.
30–200 APublished current choices
0.1 µΩMinimum resolution
0–20 mΩPublished maximum span at 30 A
Lithium batteryPublished power route
High-output AC route
RDHL-200X
Loop Resistance Tester
An AC-powered route with a published output voltage up to 10 V, multiple current levels and timed tests for demanding on-site or production work.
25–200 APublished current choices
Up to 10 VPublished output voltage
0.1 µΩMinimum resolution
AC 220 VPublished supply
Continuous measurement route
RDHL-100A / RDHL-200A
Loop Resistance Tester
A continuous-measurement platform with 50 A and 100 A options, plus 150 A and 200 A selections on the RDHL-200A version.
50–200 AModel-dependent current choices
0.1 µΩMinimum resolution
7-inchPublished touch display
1,000 setsPublished result storage
Selection note: resistance range changes with selected current. Confirm the required current, useful resistance span at that current, output duration, lead length and cross-section, clamps, battery or mains supply, printer, interfaces, language and calibration documents before ordering.
Start with the field constraint
Choose the equipment route from power, duty and expected resistance
Portable substation route
Prioritize battery operation, manageable leads, transport protection, fast setup and enough charge for the planned breaker list.
Higher-output route
Consider available output voltage, current stability, range at the chosen current and site mains when long leads or difficult circuits are expected.
Repeatable record route
Prioritize stored asset identifiers, current and time settings, USB or other interfaces, printout needs and a consistent report structure.
Compare published configurations
Match current, range and duty before comparing convenience features
A larger maximum current does not automatically fit every job. Read each published resistance range at the intended current, then confirm the approved method and final configuration with Wrindu.
| Selection field | RDHL-200HX | RDHL-200X | RDHL-100A / RDHL-200A | Procurement meaning |
|---|---|---|---|---|
| Published test current | 30, 50, 80, 100, 150, 200 A | 25, 50, 100, 150, 200 A | 100A model: 50, 100 A; 200A model: 50, 100, 150, 200 A | Match the specified current rather than choosing only by the largest headline value. |
| Published resistance range | 20 mΩ at 30 A down to 1 mΩ at 200 A | 50–300 mΩ at 25 A; 0–10 mΩ at 200 A, with intermediate ranges | 0–100 mΩ at 50 A; model-dependent ranges down to 0–20 mΩ at 200 A | Verify that the expected contact resistance sits inside the range for the selected current. |
| Resolution / accuracy | 0.1 µΩ; ±(0.5% rdg + 1 µΩ) | 0.1 µΩ; ±(0.5% rdg + 1 µΩ) | 0.1 µΩ; ±(0.5% ± 2 digits) | Resolution is display granularity; evaluate accuracy, repeatability and the complete setup separately. |
| Published operating route | Rechargeable lithium battery; fast or timed selections, with timing listed for 30–100 A | AC 220 V; fast or 10–60 s selections | AC 220 V; continuous measurement | Site power and required output duration can determine the practical choice. |
| Best early fit | Portable field rounds and locations where battery operation reduces setup constraints | AC-powered work needing the published 10 V maximum output and wider current-specific ranges | Routine continuous-measurement workflow with model choice around 100 A or 200 A ceiling | Final fit depends on asset list, leads, clamps, duty, environment and report requirements. |
| Product details | Open RDHL-200HX | Open RDHL-200X | Open RDHL-100A/200A | Request the latest technical sheet and itemized supply list before purchase. |
Separate current from voltage sensing
Four-terminal placement protects a micro-ohm result from lead resistance
Outer pair: current injection I+ / I−Inner pair: voltage sensing V+ / V−Sense points bracket the contact pathClamps sit on clean, secure conductors
The instrument measures a small voltage drop inside a known current path
Current leads carry the test current. Separate sense leads observe the voltage drop across the intended section. The tester calculates resistance from those two quantities.
- Confirm the breaker is isolated, discharged and in the authorized closed state.
- Place the voltage sense points inside the current connections around the intended contact path.
- Keep polarity, connection locations and lead routing consistent across repeated tests.
- Do not interpret a result until the approved procedure, temperature context and comparison basis are defined.
A visible four-step selection method
How to select circuit breaker contact resistance test equipment
Use these procurement steps before requesting a quotation. They are also represented in the page's HowTo structured data.
Define the asset list
List breaker models, poles, contact paths, expected resistance and the site or factory environment.
Fix current and duty
Record the approved test current, output duration, repeat count and useful resistance range at that current.
Specify connections
Confirm lead length, conductor size, Kelvin clamps, terminal access, polarity and safe working distance.
Define deliverables
Request the needed storage, printout, USB or software route, calibration documents and supplied accessories.
Keep each landing page's job distinct
Static contact resistance is not breaker timing or a complete maintenance plan
This page owns the closed main-circuit measurement
Use it for static micro-ohm contact resistance, test current, current-specific range, output duty, four-terminal leads, field power and result records.
Dynamic and broader questions stay elsewhere
Opening/closing time, synchronism, travel and speed belong to the timing page. A multi-instrument maintenance scope belongs to the maintenance page. General breaker categories remain on the parent page.
Prepare a useful inquiry
Send the test current, expected range and connection constraints
Breaker and method
- Manufacturer, model, voltage class and interruption medium
- Poles, breaks per pole and exact contact path
- Required test current, duration and repeat count
- Expected resistance range and comparison criteria
- As-found, after-service, commissioning or production context
Equipment and deliverables
- Battery or AC supply and site plug requirements
- Lead lengths, conductor size, Kelvin clamps and terminal access
- Storage, printer, USB, software and report fields
- Language, calibration certificate and required standards
- Case, accessories, quantity and delivery schedule
Contact resistance tester FAQ
Questions to settle before selecting a micro-ohm tester
What does circuit breaker contact resistance test equipment measure?
It injects a known current through the closed breaker contact or main conducting path, senses the small voltage drop across that path and calculates resistance, normally in micro-ohms. The result supports comparison with the approved acceptance or maintenance basis when asset state and test conditions are controlled.
Why is a four-terminal or Kelvin connection used?
Separate current and voltage-sense connections prevent most test-lead resistance from being included in the measured contact path. The sense points must bracket the intended section, while the current clamps sit outside them and provide a stable current path.
Should a 100 A or 200 A contact resistance tester be selected?
Select the current required by the breaker procedure, customer specification or applicable authority. Then check the instrument's resistance range, accuracy and permitted duration at that current. A 200 A maximum alone does not prove that a tester is the correct choice for every breaker.
What is the difference between static and dynamic resistance measurement?
Static contact resistance is measured with the main contacts closed in a defined stationary condition. Dynamic resistance records resistance behavior during contact motion and needs synchronized operation and analysis capability. This page focuses on static contact or loop resistance; use the timing analyzer page for dynamic breaker behavior.
What information is needed for a contact resistance tester quotation?
Provide the breaker models and contact paths, required current and duration, expected resistance range, site power, lead length and clamps, battery requirement, test volume, storage and reporting needs, language, calibration documents, accessories and delivery schedule.
Compare the tester against the real breaker path and field workflow
Send Wrindu the asset list, test current, expected resistance, duty, lead requirement, site power and reporting needs. The technical team can help shortlist the appropriate RDHL configuration.
Technical parameters shown here are based on public HVTesters product information reviewed on 29 August 2026. Confirm the current model, specifications, leads, clamps, accessories, calibration documents and approved test method before purchase or use.
Know more / technical selection notes
Understand the measurement before comparing the micro-ohm tester
This expanded guide supports engineers and buyers who need more context than a model table. It explains the measurement boundary, four-wire connection, current and duty choices, repeatability and the information needed for a technically useful quotation.
Know More: Contact resistance measurement, equipment selection and reporting
Static contact resistance describes a closed conducting path
A circuit breaker contact resistance test applies current through a selected main conducting path while the breaker is closed and stationary. The instrument measures the small voltage drop between defined sense points and calculates a resistance value. For a high-voltage breaker, that path may include terminals, joints, moving and fixed contacts and other internal connections. The record therefore needs to identify exactly what was included between the voltage leads.
The measurement is useful for commissioning baselines, routine condition comparison, after-maintenance verification and production checks. It does not by itself identify the location or cause of every abnormal value. Investigation may need inspection, repeat measurements, comparison across phases or poles, review of contact pressure and mechanism condition, thermal evidence or other approved tests.
Static result
A value recorded with the selected contact path closed and mechanically stationary under a defined test current and connection arrangement.
Dynamic result
A resistance trace captured while contacts move. It requires synchronized operation and analysis capability and is outside this page's primary equipment scope.
Why a Kelvin connection matters at micro-ohm levels
Ordinary two-wire resistance measurement includes the resistance of the test leads and connections in the same voltage reading as the object under test. At micro-ohm levels, that unwanted contribution can be much larger than the contact resistance being investigated. A four-terminal arrangement separates the current circuit from the voltage-sense circuit.
Icontrolled test current
→Vmeasured voltage drop
→R = V / Icalculated resistance
- The outer connections carry the high test current through the selected path.
- The inner sense points measure voltage across the part of the path that the record is intended to represent.
- Sense leads draw negligible current, so their own resistance has little effect on the voltage reading.
- Reversing, moving or contaminating connections can change the measured path and reduce comparability.
Practical meaning: buying a tester with 0.1 µΩ resolution does not create a 0.1 µΩ-quality field result by itself. Connection quality, current stability, sense-point placement, asset condition and the approved method remain part of the measurement system.
Select test current, resistance range and output duty together
Test current is not an isolated specification. Each tester publishes a resistance range for particular current settings, and some instruments allow a current only for a limited duration. Begin with the method or project requirement, then read the instrument specification at that exact current.
Current requirement
Record the prescribed current and whether the procedure allows a choice. Do not replace an approved value solely because another setting is more convenient.
Useful range
Confirm that the expected resistance falls within the range published for the chosen current, not simply within the tester's broadest range.
Output duration
Check fast, timed or continuous operation, allowed duration at each current and the cooling or waiting interval between repeated tests.
Available voltage
Long leads and circuit resistance create voltage demand. Confirm output capability and lead arrangement for the actual field geometry.
RDHL-200HX publishes current selections from 30 A to 200 A, with timed selections specified for 30 A through 100 A. RDHL-200X publishes 25 A through 200 A, an output voltage up to 10 V and timed selections. RDHL-100A/200A publishes continuous measurement with current choices determined by model. These distinctions are more useful than comparing the shared 200 A headline alone.
A controlled setup makes repeated values easier to interpret
Field conditions can change between measurements even when the breaker has not changed. A repeatable work instruction should address safety isolation, breaker state, surface condition, connection points, lead routing, selected current, stabilization, temperature context and asset labeling.
Before current is applied
- Confirm isolation, discharge, grounding and work authorization under the site's safety procedure.
- Identify the exact pole, phase, break and terminal-to-terminal path.
- Inspect test leads, current clamps, sense clips, insulation and connectors for damage or contamination.
- Place voltage sense connections inside the current connections around the intended measured path.
- Verify instrument supply, battery state, current selection, range, timing and record identifier.
While the value is recorded
- Observe current stability and the instrument's alarms rather than recording the first number automatically.
- Follow the permitted output time and do not exceed the tester or test-object duty.
- If a result is repeated, preserve the same connection points and state or document what changed.
- Stop and investigate unstable connections, unexpected heating, alarms or results outside the authorized process.
Comparable records explain more than a list of micro-ohm values
A useful baseline keeps the measurement result attached to the conditions that created it. Without that context, later teams may compare unlike poles, different current settings or different voltage-sense locations and incorrectly treat the difference as equipment deterioration.
Asset identity
Substation, bay, breaker manufacturer/model, serial number, pole, phase, break and terminal path.
Asset state
Commissioning, as-found, after-service or production stage; closed condition and relevant maintenance action.
Test setup
Tester serial/calibration, test current, duration, current and sense locations, lead set and selected mode.
Result context
Resistance, stability or repeats, ambient/asset temperature where required, operator, date and review status.
Acceptance criteria should come from the project authority, asset manufacturer, applicable procedure or other approved source. A landing page and a product specification can help select equipment, but neither should invent a universal pass/fail limit for every breaker design.
Current-specific model matrix for early procurement planning
The matrix summarizes published routes checked on 29 August 2026. It is not a substitute for the current product datasheet or quotation.
| Published field | RDHL-200HX | RDHL-200X | RDHL-100A / RDHL-200A |
|---|---|---|---|
| Product route | Portable loop resistance tester | Higher-output loop resistance tester | Continuous-measurement loop resistance tester |
| Current choices | 30, 50, 80, 100, 150, 200 A | 25, 50, 100, 150, 200 A | 50 and 100 A on RDHL-100A; 50, 100, 150 and 200 A on RDHL-200A |
| Published range examples | 0–20 mΩ at 30 A; 0–5 mΩ at 100 A; 0–1 mΩ at 200 A | 50–300 mΩ at 25 A; 0–50 mΩ at 100 A; 0–10 mΩ at 200 A | 0–100 mΩ at 50 A; 0–50 mΩ at 100 A; 0–20 mΩ at 200 A on RDHL-200A |
| Published resolution | Minimum 0.1 µΩ | Minimum 0.1 µΩ | Minimum 0.1 µΩ |
| Published accuracy | ±(0.5% rdg + 1 µΩ) | ±(0.5% rdg + 1 µΩ) | ±(0.5% ± 2 digits) |
| Power / duty route | Rechargeable battery; fast and timed selections, with timed mode published for 30–100 A | AC 220 V; fast or 10–60 s selections; published output voltage up to 10 V | AC 220 V; continuous measurement |
| Data points to confirm | Battery endurance, charging, optional printer, USB, leads and high-current duty | Site supply, lead requirement, output time, storage, printing and communication | Exact model, current ceiling, storage/interface configuration, leads and accessories |
Do not confuse contact resistance with three adjacent test categories
Breaker timing and travel
Measures when contacts change state and how the mechanism moves. Use circuit breaker timing test equipment.
Dynamic resistance
Records resistance during contact motion and requires synchronized operation. It is not the same as a static closed-contact reading.
Insulation resistance
Uses high DC test voltage and very low current to evaluate insulation behavior, producing megohm or higher readings rather than micro-ohm conductor values.
Earth loop / grounding
Evaluates protective earthing or fault-loop conditions. Similar use of the word “loop” does not make an earth-loop tester suitable for breaker main-contact resistance.
For the wider equipment context, return to circuit breaker testing equipment. For a multi-instrument service scope, use the dedicated circuit breaker maintenance test equipment page.
Copy this information into a technical inquiry
A structured request allows the supplier to compare current, range, duty and accessories against the actual job.
Application: circuit breaker static contact / main-loop resistance
Breaker manufacturer and model:
Voltage class and interruption medium:
Number of breakers, poles and breaks per pole:
Exact terminal-to-terminal measurement path:
Required test current(s):
Required output duration and repeat count:
Expected resistance range:
Site power available / battery operation required:
Lead length, conductor size and clamp requirement:
Storage, printer, USB or software requirement:
Language and report fields:
Calibration documents / referenced procedure:
Required accessories, quantity and delivery date:Safety and acceptance note: testing must follow the asset manufacturer's instructions, applicable standards, the site's isolation and grounding rules and the project authority's approved method. Confirm current specifications and supplied accessories before procurement.