Shunts

Electrical shunts play a vital role in precise current measurement across a wide range of applications. Whether you're working in industrial automation, automotive systems, or scientific instrumentation, the right shunt resistor enables accurate monitoring and control of electrical currents. A current shunt—also referred to as a current measuring shunt or current shunt resistor—works by producing a small voltage drop proportional to the current flow, allowing for high-precision readings without significant power loss.

From compact precision shunt resistors to robust high current shunt resistors, selecting the appropriate type is key to performance and reliability in your system. Understanding their functions, types, and applications helps ensure optimal integration into your electrical setup.

What are Shunt Resistors?

A shunt resistor, also known as a current shunt resistor or ammeter shunt, is a low-resistance component designed to measure current flow by producing a small, precise voltage drop. This drop—calculated using Ohm’s Law (V = IR)—is directly proportional to the current passing through the resistor and is used by meters or monitoring devices to determine the actual current in amperes.

In many setups, a precision shunt resistor is connected in series with the load. In some applications, it may also be placed in parallel with a measuring instrument like an ammeter to allow only a small fraction of the current to pass through the meter itself. This protects the device while still allowing accurate current measurement.

How Does It Work?

Voltage Drop Principle: Shunt resistors work by producing a small voltage drop across a known, low-resistance path when current flows through it. According to Ohm’s Law (V = IR), this drop is directly proportional to the current, allowing accurate measurements without significant energy loss.

• Series Placement in the Circuit: To ensure full current flow through the current shunt, it must be connected in series with the load. This placement allows precise voltage readings across the resistor’s terminals while minimising power disruption to the rest of the circuit.
• Non-Intrusive Measurement: The voltage drop is captured by monitoring equipment such as ammeters or digital control modules. This enables real-time current tracking without affecting the operation of the system—ideal for sensitive or continuous processes.
• Applications in DC and AC Circuits: While commonly used as DC current shunts in solar systems or EV batteries, many shunt resistors also support AC current monitoring, depending on design. Their versatility makes them essential for industries like automotive, energy, and manufacturing.

Types of Electrical Shunts

Different types of electrical shunts are engineered to serve specific performance requirements based on application needs, power ratings, current ranges, and environmental conditions. Whether you're designing a high-precision monitoring system or need to handle large current loads in industrial setups, selecting the right current shunt resistor is essential.

Below, we break down the most common categories of shunt resistors, including precision current shunts, high current shunt resistors, and DC current shunts, along with their technical specifications and ideal use cases for B2B buyers.

Precision Shunt Resistors & Precision Current Shunts

These are ultra-accurate, low-resistance shunt resistors designed for high-precision current measurement in sensitive electrical circuits.

• Resistance Value: Extremely low, often in the milliohm range (e.g., 0.001Ω to 0.1Ω), to minimise voltage drop while still enabling precise measurements.
• Tolerance: Very tight tolerance levels, typically ±0.1% or better, ensuring high measurement reliability.
• Temperature Coefficient: Low TCR values, as low as ±15 ppm/°C, to maintain accuracy even with temperature fluctuations.
• Power Rating: Designed to handle moderate loads, ranging from 0.25W to a few watts depending on application requirements.
• Material Composition: Often made with manganin or similar materials for stable resistance across a wide temperature range.
• Form Factor: Available in surface-mount and through-hole configurations for integration in compact systems.
• Ideal Use For: Laboratory-grade power supplies, calibration instruments, high-accuracy multimeters, and data acquisition systems in medical, aerospace, or test and measurement fields.

High Current Shunt Resistors

These are robust, high-power resistors built to handle large currents while maintaining accuracy and durability in demanding environments.

• Resistance Value: Very low (micro-ohms to low milliohms), to ensure minimal voltage drop even under high current flow.
• Current Rating: Capable of measuring currents from tens to thousands of amperes, depending on size and model.
• Power Rating: High power dissipation capability, often ranging from 5W up to several hundred watts.
• Construction: Built with heavy-duty terminals and solid metal bars or slabs for heat resistance and mechanical stability.
• Mounting: Often bolted or clamped onto busbars or panels; some models include integrated cooling fins.
• Ideal Use For: Industrial power distribution units, battery testing stations, large inverter systems, and electric vehicle load monitoring setups.

DC Current Shunts

DC current shunts are designed specifically for measuring direct current. They are calibrated for high-load, stable DC environments and are commonly found in power infrastructure systems.

• Resistance Value: Extremely low, often in the range of 50µΩ to 500mΩ, depending on current range requirements.
• Voltage Output: Typically designed to output a precise voltage (e.g., 50mV or 75mV) at rated current for easy interfacing with monitoring equipment.
• Current Rating: Often ranges from 10A to 1000A or more.
• Mechanical Design: Metal bar construction, frequently enclosed for safety and stability, especially in rugged industrial settings.
• Calibration: Usually factory-calibrated for high repeatability and long-term stability in DC applications.
• Ideal Use For: Solar power systems, battery banks, UPS units, marine electrical setups, and railway traction systems.

Difference Between Precision Shunt Resistors and DC Current Shunts

A precision shunt resistor is built for high-accuracy current measurement and may be used in both AC and DC systems, especially in laboratory, test, and instrumentation setups. Its key advantage lies in its extremely low tolerance and temperature coefficient, which allows for highly accurate, repeatable readings, even with fluctuating loads or environmental changes.

In contrast, a DC current shunt is tailored specifically for use in direct current environments. While it may still be precise, its design prioritises stability, durability, and ease of installation in large-scale, high-current DC systems. These are more commonly found in practical power applications such as solar arrays, battery storage systems, and heavy-duty industrial DC networks.

Key Factors to Consider When Choosing Electric Shunts

Selecting the right electrical shunt is crucial to ensuring accurate measurement, system safety, and long-term performance. Each factor plays a role in determining whether the shunt will meet your application's electrical and environmental demands.

• Resistance Value: The core of how a shunt works—lower resistance values produce lower voltage drops. Choose a resistance that balances sensitivity with power efficiency.
• Tolerance and Accuracy: Tighter tolerances (e.g., ±0.1%) offer more precise current measurements. This is essential for critical systems like instrumentation or calibration.
• Power and Voltage Ratings: Make sure the shunt can safely dissipate heat under expected loads and withstand the circuit’s operating voltage without risk of damage.
• Current Rating: The shunt must be rated for the maximum current it will measure. Underrated shunts can overheat or provide inaccurate readings.
• Environmental Conditions: Temperature, humidity, vibration, and dust can affect shunt performance. Choose ruggedised or enclosed models for harsh environments.

Mistakes to Avoid When Buying Electrical and Current Shunts

Avoiding common pitfalls when selecting a current shunt can save both time and cost, while also preventing safety issues or faulty readings.

• Choosing the Wrong Shunt Resistor Value: A shunt with a resistance too high may create excessive voltage drop and power loss, while one too low may not produce a readable signal.
• Ignoring Tolerance Requirements: Especially in measurement-critical applications, using a high-tolerance shunt can lead to inaccurate data and unreliable system behavior.
• Failing to Consider Power Ratings: Shunts must dissipate power as heat; choosing one with insufficient wattage capacity can result in overheating or resistor failure.
• Overlooking Voltage Rating: In high-voltage systems, using a shunt with inadequate insulation or voltage tolerance can pose a serious safety risk or cause component failure.

Industry Applications

Electrical shunts are vital in ensuring precise current measurement across diverse sectors. Their ability to provide reliable real-time data makes them indispensable in both commercial and industrial settings.

Automotive

In the automotive industry—especially in electric and hybrid vehicles—current shunts are widely used to monitor battery charge and discharge cycles. These shunts are typically integrated into EV powertrains, where they measure the flow of current between the battery pack and motor controller. This real-time current data is vital for ensuring optimal battery usage, managing regenerative braking, and improving vehicle performance and range.

Renewable Energy

Within renewable energy systems, DC current shunts are essential for monitoring the output of solar inverters and the performance of battery storage units. In off-grid and hybrid solar installations, they allow operators to measure load currents accurately and optimise charging cycles. This ensures energy generated by solar panels is stored and used efficiently, while also protecting batteries from overcharging or excessive discharge.

Manufacturing & Industrial Systems

In heavy industrial environments, high current shunt resistors help manage and monitor the power draw of large motors and machinery. Installed within motor drives and power control units, these shunts enable precise load measurement, prevent equipment overload, and support energy optimisation across factory floors. Their ability to handle high currents makes them ideal for manufacturing systems where safety and uptime are critical.

Electronics & Instrumentation

For electronic testing and measurement, precision shunt resistors are indispensable tools. These ultra-low resistance components are commonly found in lab-grade multimeters, oscilloscopes, and other test equipment used for capturing low-current signals with high accuracy. Whether in R&D labs or quality control environments, they ensure that every microampere is measured with precision, supporting the development of reliable and efficient electronic devices.

Your Trusted Electrical Shunts Supplier & Manufacturer in Australia

RS is a leading supplier of electrical shunts, including shunt resistors, DC current shunts, and high current shunt resistors, serving engineers and businesses across Australia. We stock products from top brands like Bourns, HOBUT, and Socomec—ensuring high-quality solutions that meet international standards.

Beyond shunt solutions, we also offer a broad selection of complementary components such as vibration meters, motor controllers and other electrical system essentials—helping you streamline procurement and system integration in one place. For delivery details, shipping times, and service options, please visit our Delivery Page.