EN
DRM-20 Single-Channel DC Resistance Tester
DRM-20 Digital Intelligent Single-Channel DC Resistance Tester (20A Max Current) with 0.1μΩ Resolution, 4-Wire Kelvin Measurement, Auto Back-EMF Protection, Copper/Aluminum Temperature Conversion, 1000 Groups Data Storage, for 35kV-110kV Transformer Winding, Motor Winding, Instrument Transformer, Switch Contact Resistance Test.
- Description
- Specifications
- Applications
- Advantages
- FAQ
- Recommended Products
Description
The DRM-20 is a high-precision, cost-effective single-channel DC resistance test instrumentexclusively designed for fast and accurate measurement of DC resistance in medium and large inductive loads. It fully complies with DL/T 845.3-2019 and GB 50150-2016 standards, adopting advanced constant current source technology and 4-wire Kelvin measurement method to eliminate lead resistance and contact resistance errors, replacing traditional DC single and double arm bridges.
The instrument features a 5.6-inch high-brightness industrial LCD screen and intuitive keypad operation, supporting both fixed current and automatic current selection modes. It has a built-in fast charge/discharge circuit that can stabilize readings within 3 seconds, and a comprehensive back-EMF protection system to ensure operator and equipment safety. It supports copper/aluminum temperature automatic conversion, 1000 groups of data storage, and USB data export. With AC220V power supply and optional built-in lithium battery, it is suitable for both laboratory and on-site testing. Ideal for factory acceptance tests (FAT), on-site commissioning tests and preventive maintenance tests of 35kV-110kV power transformers, motors, instrument transformers, switches, cables and busbars.
Specifications
| Parameter | Specification |
|---|---|
| Maximum Output Current | 20A |
| Current Gears | 1mA, 10mA, 100mA, 1A, 5A, 10A, 20A (auto/manual selection) |
| Measurement Range | 20A: 0.1μΩ – 1Ω 10A: 0.5μΩ – 2Ω 5A: 1μΩ – 4Ω 1A: 10μΩ – 20Ω 100mA: 100μΩ – 200Ω 10mA: 1mΩ – 2kΩ 1mA: 10mΩ – 20kΩ |
| Resolution | 0.1μΩ |
| Accuracy | ±0.2% of reading ± 2 digits (full range) |
| Measurement Method | 4-wire Kelvin measurement |
| Stabilization Time | ≤3 seconds |
| Temperature Conversion | Copper (20℃/75℃), Aluminum (20℃/75℃) automatic conversion |
| Data Storage | 1000 groups (with time stamp, power-off protection) |
| Data Export | USB interface, PDF/Excel report generation |
| Display | 5.6-inch high-brightness industrial LCD screen |
| Power Supply | AC 220V±10%, 50Hz (standard) + optional built-in 7.4V/6Ah lithium battery |
| Battery Life (Optional) | >4 hours continuous operation at 10A output |
| Charging Time (Optional) | ~3 hours (full charge) |
| Protection Functions | Back-EMF protection, Over-current protection, Over-temperature protection, Short-circuit protection, Reverse polarity protection |
| Dimensions (mm) | 380×320×180 (L×W×H) |
| Weight | ~7kg (including accessories) |
| Operating Temperature | -10℃ ~ +50℃ |
| Operating Humidity | ≤90%RH (non-condensing) |
| Altitude | ≤2000m |
| Compliance | DL/T 845.3-2019, GB 50150-2016, IEC 60076-1:2022, IEC 60404-2:2008 |
Applications
Core Test Objects
- Power transformers: 35kV-110kV oil-immersed power transformers (up to 63MVA)
- Distribution transformers: 10kV/35kV oil-immersed and dry-type distribution transformers
- Electric motors: medium and large synchronous motors and induction motors
- Instrument transformers: current transformer (CT) and voltage transformer (VT) winding test
- Low-voltage switchgear: circuit breaker, contactor, relay contact resistance test
- Power cables and busbars: conductor DC resistance test
- Welding points: weld quality inspection
- Reactors: shunt reactor and series reactor winding test
Typical Usage Scenarios
- Transformer manufacturing plants: factory acceptance tests (FAT) of medium and large transformers
- Power companies: on-site commissioning tests and preventive maintenance tests
- Motor manufacturing plants: motor winding quality inspection
- Third-party testing laboratories: compliance testing and certification
- Mining and industrial enterprises: equipment inspection and maintenance
- Technical schools and universities: teaching and demonstration experiments
Advantages
Compliance with International Standards
Fully meets DL/T 845.3-2019, GB 50150-2016 and IEC 60076-1 standards → test results are globally recognized
20A High-Current Output
Larger test current than 10A models → faster charging of large inductive loads, more stable readings for low resistance measurements
Ultra-High Precision & Sensitivity
0.1μΩ resolution and ±0.2% accuracy → detects minute resistance variations caused by poor welding, loose connections and broken strands
3-Second Fast Test
Advanced fast charge/discharge circuit → improves test efficiency by 80%, reduces test time from minutes to seconds
Comprehensive Safety Protection
Automatic back-EMF protection and discharge indication → maximum safety for operators and expensive test equipment
Portable & Flexible Power Supply
7kg lightweight design with optional built-in battery → suitable for both laboratory and on-site testing
Intelligent Data Management
Automatic temperature conversion, 1000 groups data storage and USB export → eliminates manual recording errors, improves data traceability
High Cost-Effectiveness
High performance at a competitive price → ideal for small and medium-sized transformer manufacturers and field test teams
FAQ
Q: What is the difference between DRM-20, DRM-10W and DRM-20S?
A:
- DRM-20 (Single-Channel 20A): 20A maximum current, single-channel test, AC power supply (optional battery), optimized for 35kV-110kV medium and large transformers, cost-effective
- DRM-10W (Single-Channel 10A): 10A maximum current, built-in 8-hour battery, portable design, optimized for 10kV/35kV distribution transformers and remote on-site testing
- DRM-20S (Three-Channel 20A): Three-channel synchronous test, magnetic assist technology, automatic demagnetization, on-load tap changer test mode, optimized for 110kV/220kV large power transformers and high-volume production lines All three use 4-wire Kelvin measurement and have the same ±0.2% measurement accuracy.
Q: What is the advantage of 4-wire Kelvin measurement over 2-wire measurement?
A: 2-wire measurement includes the resistance of the test leads and contacts in the result, which can cause significant errors for low resistance measurements. 4-wire Kelvin measurement uses two separate pairs of leads: one pair to supply current and the other pair to measure voltage, completely eliminating lead and contact resistance errors. This is essential for accurate measurement of low resistances below 1Ω.
Q: Can DRM-20 test inductive loads such as transformer windings?
A: Yes. It is specifically designed for inductive load testing. It has a built-in fast charge/discharge circuit and comprehensive back-EMF protection system that can safely absorb the reverse electromotive force generated by inductive loads during discharge, preventing damage to the instrument and ensuring operator safety.
Q: How long does it take to test a 110kV transformer winding?
A: With the advanced fast charge/discharge circuit and 20A high-current output, the instrument can stabilize readings within 3-5 seconds for most 110kV transformer windings, which is 50% faster than 10A models and 80% faster than traditional DC bridges.
Q: Does it support data storage and export?
A: Yes. It can store 1000 groups of test data with time stamp (power-off protection). The data can be exported to a USB flash drive in PDF or Excel format for further analysis and report generation.
