A shunt resistor is a low resistance resistor specifically designed for precise measurement of current. Its core function is to indirectly calculate the current value by measuring the small voltage drop generated when the current flows through it (following Ohm's law \ (V=I \ times R \)). The following are its key features and design details:
Physical Structure and Materials
Low resistance design: The resistance value is usually in the range of milliohms (m Ω) to micro ohms (μ Ω), such as 0.1m Ω or 500 μ Ω, to reduce power loss and heat generation when current flows through.
Special alloy material: made of Manganin, Constantan, or nickel chromium alloy, with an extremely low temperature coefficient (TCR, such as ± 25 ppm/° C), ensuring stable resistance during temperature changes.
Large sized conductors: To carry high currents, resistors often use flat metal strips, thick film printing, or alloy wire structures, and optimize heat dissipation through large-area solder pads or metal substrates (such as copper).
Typical appearance and packaging
SMD (Surface Mount Device): Designed for miniaturization (such as 2512, 2010 package), suitable for PCB integration, such as Rohm's GMR series.
Modular/Busbar Integration: High power models (such as Bourns' Riedon series) use copper bars or bolt fixed structures, which can be directly installed on power busbars or busbars, supporting thousands of amperes of current.
Four terminal structure (Kelvin connection): eliminates the influence of wire resistance on measurement accuracy through independent voltage detection pins and current input pins.
Working principle
Current shunt: By connecting resistors in parallel in the circuit under test, most of the current flows through the shunt, and the resulting voltage drop (V=I \ times R) is read by a precision amplifier or ADC.
Low self heating effect: By optimizing materials and heat dissipation design, reducing temperature rise caused by current and avoiding resistance drift.
The core difference from ordinary resistors
|Characteristics | Diverter Resistance | Ordinary Resistance|
|Resistance range | 0.01m Ω~100m Ω (extremely low resistance) | 1 Ω~10M Ω (medium high resistance)|
|Accuracy | ± 0.1%~± 1% (ultra-high accuracy) | ± 1%~± 10% (conventional accuracy)|
|Power carrying capacity | 1W~1000W (high power density) | 0.1W~10W (conventional power)|
|Application purpose | Current detection, energy metering | Current limiting, voltage division, signal matching|
Typical application scenarios
New energy vehicles: Charge and discharge current monitoring in battery management system (BMS).
Industrial equipment: Real time current protection for frequency converters and motor drives.
Solar inverter: current collection and efficiency optimization of photovoltaic arrays.
Consumer electronics: fast charging for mobile phones, power management for laptops.
Key parameters for selection
Resistance accuracy: ± 0.1% is suitable for precision instruments, ± 1% is suitable for industrial control.
Rated power: It needs to be calculated based on the maximum current \ (I2 {max} \) (P=I ^ 2 \ times R \).
Temperature coefficient (TCR): Products below ± 50 ppm/° C should be selected for high temperature environments.
Packaging compatibility: Surface mount design is suitable for compact designs, while bolt mount design is suitable for high current scenarios.
Example: Automotive grade shunt resistor (such as Rohm GMR 320)
Parameters: Resistance 0.5m Ω, Power 10W, TCR ± 50 ppm/° C, AECQ200 certification.
Structure: Four terminal patch package (7.1mm × 4.2mm), with a manganese copper alloy laminated structure inside, and heat dissipation through a copper substrate.
Diverter resistor is a precision device optimized for current detection, which has become an indispensable "current sensor" in power electronic systems due to its low resistance, high power, and low temperature drift characteristics. The core of its design lies in balancing measurement accuracy and power consumption, and adapting to the full scene requirements from microampere to kiloampere level.