Handheld Loop Resistance Tester – 100A DC

The MOEORW-WKH100C Loop Resistance Tester (also referred to as a Contact Resistance Tester, High-Current Micro-Ohmmeter, or Heavy-Current Resistance Measuring Instrument) is a next-generation portable testing device designed in strict accordance with DL/T 845.4-2022 "General Technical Specifications for Resistance Measuring Devices" and SD301-88 "AC 500kV Electrical Equipment Handover and Preventive Test Procedures." It is more than a conventional micro-ohmmeter-it is a high-current resistance detector capable of actively penetrating oxide films on contact surfaces.

In power systems, the loop resistance of circuit breakers, disconnectors, and similar equipment is a critical indicator of their operational health. Abnormally high resistance values indicate poor contact, which can lead to localized overheating and even burnout over extended operation. This instrument delivers a pure DC test current of ≥100A, forcefully penetrating the insulating oxide layer on contact surfaces to obtain the true metallic contact resistance, thereby providing a reliable basis for equipment condition assessment.

Why is 100A high current essential? According to Joule's law, oxide films undergo soft or thermal breakdown under high current density. Only under this condition does the measured resistance represent the genuine "loop resistance" rather than the "film resistance." Low-current measurements (a few amperes or even milliamperes) may only capture the insulation resistance of the oxide layer, with errors potentially reaching severalfold to tens of times-this is the fundamental distinction between this instrument and ordinary multimeters or low-end milliohmmeters.

Understanding "rdg ± 1 μΩ": "rdg" denotes reading error, while "1 μΩ" is a fixed base error. For instance, when measuring 100μΩ, the absolute error is 100×0.5% + 1 = 1.5μΩ, meaning the true value lies between 98.5μΩ and 101.5μΩ-this accuracy level fully satisfies the handover acceptance standards for 110kV and above circuit breakers.

The instrument employs a four-terminal Kelvin measurement architecture internally, featuring two independent terminal sets on the front panel:

• C1/C2 (Current Output Terminals) – Connect to the thicker cables in the test lead set, delivering the 100A high current to the device under test (DUT).
• P1/P2 (Voltage Input Terminals) – Connect to the thinner cables, solely sampling the voltage drop across the DUT.
• The voltage measurement loop has an input impedance of several megaohms, with current flow at the microampere level. Consequently, the resistance of the test leads themselves (even at 6 meters in length with slight bends) and the contact resistance between the clamps and the DUT do not enter the voltage measurement circuit. The final resistance value is calculated as Voltage / 100A (constant current value), independent of lead resistance-this is the fundamental distinction that sets this professional switch loop resistance detector apart from ordinary low-resistance meters.
• Operational verification method: Users can perform a simple experiment-measure the same contact point using brand-new test leads and then again using aged leads; the readings should remain essentially consistent, intuitively validating the four-wire system's immunity to lead resistance.

1. One-Touch Smart Testing – No Zero Adjustment Required
After power-on, no manual potentiometer adjustment is needed. Simply configure the current range and duration via the on-screen menu, then press 【OK】 to start the test. The reading auto-locks upon stabilization; press 【OK】 again to stop and enter the print/save selection interface. The absence of mechanical potentiometers eliminates zero drift caused by vibration-a critical advantage for mobile inspection vehicles.

2. On-Site Data Storage & Multiple Export Options
Built-in front-loading micro-printer: Prints test results instantly on-site (including date, current value, and resistance value) as an original record attachment, eliminating manual transcription.
Direct USB drive export: Supports FAT32-formatted USB drives; test data is saved in CSV format for Excel import and trend analysis.
Bluetooth communication (optional): With companion software, transmits data wirelessly to laptops or tablets, automatically generating A4-format reports compliant with the "Electrical Equipment Preventive Test Procedures"-particularly valuable for users required to issue formal acceptance documentation.

3. Wide-Temperature LCD & Outdoor Ruggedness
Equipped with a wide-temperature Chinese-character LCD, operational from -10°C to 40°C, the display remains legible without blackout or ghosting even under direct midday sunlight. The housing is constructed of high-strength engineering plastic, offering impact resistance and excellent insulation properties.

4. Language Toggle (Internationalization Detail)
On the main interface, pressing 【◄】 and 【OK】 simultaneously switches between Chinese and English display-facilitating operation for export shipments or when foreign supervisors are present on-site.

This instrument serves as a universal tool in electrical installation, maintenance, and testing. Typical application scenarios include:
High-voltage circuit breaker conductive loop resistance testing (measuring main contact resistance under closed status)-this is the primary design purpose and a mandatory preventive test item per DL/T 596.
Disconnector and earthing switch contact finger resistance measurement, to assess whether contact spring pressure has degraded or contact surfaces have accumulated contamination.
Busbar lapped joints, aluminum-copper transition connectors, and cable terminal crimp quality inspection, to prevent localized overheating hazards caused by poor workmanship.
Electrical equipment handover and acceptance testing, establishing baseline resistance values before new substations are commissioned-serving as "fingerprint data" for future maintenance comparison.
Post-fault re-testing, such as rapid assessment of whether contacts have welded or suffered ablation following short-circuit current surges.
Use as a high-current constant-current source, paired with an external standard shunt to expand functionality for calibrating other resistance-type sensors.
Across these scenarios, field engineers commonly refer to this instrument as a circuit breaker contact resistance meter or a portable DC high-current micro-ohmmeter. Its core value lies in accomplishing with a single handheld-grade device what previously required a bulky high-current generator and a separate millivoltmeter working in tandem.

As a professional power test instrument manufacturer, we provide the following differentiated support for B-end clients:

• Custom test lead lengths: Standard 6-meter leads are supplied; extensions to 10m or 15m are available upon request (with corresponding gauge increases to ensure current voltage drop remains within permissible limits).
• Neutral/custom branding: Supports customization of body nameplates, panel silk-screening, and outer carton printing per client brand requirements, with flexible MOQ arrangements.
• Open software protocol: Bluetooth communication protocols can be adapted to interface with client backend systems-no proprietary platform lock-in.
• Factory calibration certificate: Each instrument is accompanied by calibration records traceable to provincial-level metrology institutes, eliminating the need for secondary third-party verification upon arrival and reducing client acceptance costs.

The technical specifications listed in this document are valid as of the manufacturing date. Should future functional upgrades or appearance improvements occur, no separate notification will be issued-please refer to the actual product-however, we guarantee that core measurement performance metrics will not be downgraded.