Low Ohmic resistors are a type of resistor device with extremely low resistance, typically referring to resistors with a resistance range between milliohms (m Ω) and a few ohms (Ω). Its core design goal is to accurately measure current or achieve voltage/current division in high current paths, while minimizing the impact of its own power consumption and heat generation on the circuit. The following is a detailed analysis of low resistance resistors:
1、 The core characteristics of low resistance resistors
Extremely small resistance range
Typical resistance value: 1m Ω~1 Ω (even lower), such as the resistance value of Wangquan RN series can be as low as 2m Ω.
When current detection is achieved through a small resistance value, the voltage drop is extremely small (such as U=I × R), thereby reducing power consumption and temperature rise.
High precision and stability
The accuracy can reach ± 0.1%~± 1%, with low-temperature drift (TCR as low as ± 15ppm/℃), ensuring the accuracy of current measurement.
The materials are mostly alloys (such as manganese copper, iron chromium aluminum), which are resistant to temperature changes and mechanical stress.
High power carrying capacity
It needs to withstand high currents (such as tens of amps to hundreds of amps), and avoid overheating by optimizing the structure and heat dissipation design (such as wide electrodes and metal shells).
Low thermal electromotive force (EMF)
Use copper terminals or special alloys to reduce parasitic voltages caused by temperature gradients and avoid measurement errors.
2、 Key application scenarios for low resistance resistors
Current detection and diversion
New energy vehicles: Monitor the charging and discharging current in the battery management system (BMS) to protect the battery pack.
Motor drive: Real time detection of motor current to achieve overcurrent protection and efficiency optimization.
Power management: Current feedback control in DCDC converters and inverters.
Voltage division of high current path
In power circuits, voltage signals are obtained by voltage division through low resistance resistors, which are used to control logic or protect circuits.
Sensor signal conditioning
Coordinate with sensors (such as temperature and pressure sensors) to calibrate signals and compensate for the impact of line impedance.
3、 Technical parameters and selection points
Resistance and accuracy
Select the resistance value based on the maximum current and allowable voltage drop (for example, if the current is 100A and the resistance value is 1m Ω, the voltage drop is 0.1V and the power consumption is 10W).
High precision demand scenarios (such as BMS) require selecting ± 0.5% or higher precision.
Rated power and temperature rise
Power formula: P=I ² × R, it is necessary to ensure that the resistor can withstand the heat generated by long-term current.
Heat dissipation design: The packaging form (such as metal shell, patch type wide electrode) affects the heat dissipation efficiency.
Temperature coefficient (TCR)
Low temperature drift characteristics (such as below ± 50ppm/℃) avoid the influence of resistance changes with temperature on measurement results.
Anti-interference ability
The packaging process that is resistant to sulfurization and moisture (such as the Wangquan RL series) is suitable for harsh environments.
4、 The manufacturing difficulties of low resistance resistors
Material selection
Low resistivity and high stability alloy materials (such as manganese copper and nickel chromium alloys) are required.
Copper terminals or gold plating processes reduce contact resistance and oxidation risks.
Precision machining technology
Laser fine-tuning technology ensures resistance accuracy, and Kelvin detection eliminates lead resistance errors.
Realize miniaturization through thin film or thick film processes (such as surface mount packaging 0805, 1206).
Heat dissipation and reliability design
Optimize heat conduction through large-area metal substrates or heat dissipation pads to avoid thermal failure.
5、 Example of RALEC low resistance resistor
Taking the Wangquan RN series car standard resistors as an example:
Resistance range: 2m Ω~19m Ω, accuracy ± 0.5%~± 1%.
Power level: 1W~3W (surface mount packaging), supports high current detection.
Application scenarios: BMS for new energy vehicles, motor drive current sampling.
Technical advantages: Compliant with AECQ200 standards, resistant to sulfurization, high reliability.
Low resistance resistors are the "precision sensors" of power electronic systems, which achieve efficient and safe current monitoring and control through extremely small resistance values. Its key role in fields such as automotive electronics, industrial power supplies, and new energy has driven continuous innovation in materials, packaging, and testing technologies. When selecting, it is necessary to comprehensively weigh resistance, accuracy, power, and environmental adaptability to ensure system stability and lifespan.