# Shunt (electrical)

A shunt in electrical engineering is a low-value precision resistor placed in a circuit so that a known, controlled fraction of the current flows through it, allowing the full current to be determined from the small voltage drop across it via [Ohm's law](https://www.edgepedia.org/ohms-law). The name comes from the resistor's original role of shunting most of the current around a sensitive meter movement, and the same component, often called a current-sense resistor or shunt resistor, is now the standard sensing element in ammeters, battery monitors, motor controllers, and power supplies.

| Key fact | Detail |
|---|---|
| Function | A low resistance in parallel with a galvanometer diverts most of the current through the shunt, extending the meter's measurable range far beyond its full-scale deflection current<sup>[1](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)</sup> |
| Worked value | A 25-Ω galvanometer with 50 µA sensitivity needs a shunt of \( 1.25 \times 10^{-3} \ \Omega \) to give full-scale deflection at 1.0 A<sup>[1](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)</sup> |
| Typical resistance | Commercial shunts span from tens of micro-ohms (Bourns CSM2F-6918: 50 to 200 µΩ, 36 W) up to hundreds of ohms for small-signal use<sup>[2](https://bourns.com/products/resistors/high-power-shunts)</sup><sup> • </sup><sup>[3](https://www.campbellsci.com/products/curs100)</sup> |
| Temperature stability | Precision laboratory shunts reach temperature coefficients below 5 ppm/°C; general industrial parts range from about ±10 to ±200 ppm/°C<sup>[4](https://ohm-labs.com/precision-shunts/cs-1-10/)</sup><sup> • </sup><sup>[5](https://www.ebg-resistors.com/en/products/shunts)</sup> |
| Connection practice | A Kelvin (4-wire) connection is recommended for low-value shunts; measuring on the top pad without one produced about a 22.8% error in a documented layout test<sup>[6](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8412a.pdf)</sup> |
| Placement | High-side sensing puts the shunt between supply and load; low-side sensing puts it between load and ground, and the two differ in ground disturbance, common-mode voltage, and fault detection<sup>[7](https://www.ti.com/document-viewer/lit/html/SSZTA51/GUID-8C507D4D-FB98-422A-AF78-D19B9067D75A)</sup> |

## Operation as a meter multiplier

A galvanometer, the sensitive pointer movement at the heart of an analog meter, deflects fully at only a small current. To measure larger currents, a small shunt resistance \( R \) is connected in parallel with the galvanometer's internal resistance \( r \). Because the two are in parallel, they share the same voltage drop, so the shunt resistance is chosen from the current-divider relation \( I_{\mathrm{G}} \cdot r = (I - I_{\mathrm{G}}) \cdot R \), which gives \( R = r \cdot I_{\mathrm{G}} / I \).<sup>[1](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)</sup>

The OpenStax worked example shows how small the value becomes. A 25-Ω galvanometer with 50 µA full-scale sensitivity, converted to read 1.0 A, carries only 50 µA itself while 0.999950 A flows through the shunt, giving \( R = 25 \ \Omega \times 50 \ \mu\mathrm{A} / 0.999950 \ \mathrm{A} = 1.25 \times 10^{-3} \ \Omega \).<sup>[1](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)</sup> The larger the current to be measured, the smaller the shunt must be, and multirange ammeters switch among several shunt resistances to change scales.<sup>[1](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)</sup>

**Circuit loading.** Any meter alters the circuit it measures. An ammeter sits in series with the branch being measured, so its resistance adds to that branch; the shunt keeps this added resistance very small compared with the circuit's resistances. If an ammeter is mistakenly connected in parallel with a component, its low resistance draws most of the circuit current and can damage the meter.<sup>[1](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)</sup>

## The shunt as a current-sense resistor

In modern electronics the same principle appears as the current-sense resistor. The shunt is placed in series with the current of interest, the voltage developed across it is proportional to that current, and an amplifier or analog-to-digital converter reads the result. [Texas Instruments](https://www.edgepedia.org/texas-instruments)' high-side current shunt monitor reference design, for example, exists specifically to measure the voltage developed across a current-sensing resistor when current passes through it.<sup>[8](https://www.ti.com/tool/TIDA-00302)</sup>

**High-side versus low-side placement.** Two placements dominate practice. In low-side sensing the shunt sits between the load and ground; the common-mode voltage at the amplifier input is near zero, which keeps the amplifier simple and the cost low. In high-side sensing the shunt sits between the supply bus and the load; the amplifier must handle a common-mode voltage close to the supply, but the measurement avoids ground disturbance and can detect a load short to ground, because the full supply current still passes through the shunt.<sup>[7](https://www.ti.com/document-viewer/lit/html/SSZTA51/GUID-8C507D4D-FB98-422A-AF78-D19B9067D75A)</sup><sup> • </sup><sup>[9](https://www.ti.com/document-viewer/lit/html/SBOA165)</sup> In low-side designs, a short-circuit current that reaches ground through another path never crosses the shunt and is invisible to the amplifier.<sup>[9](https://www.ti.com/document-viewer/lit/html/SBOA165)</sup>

**Kelvin connection.** Because a shunt's resistance is often a few milliohms or less, the resistance of the copper traces and solder joints around it can rival or exceed the shunt itself. Datasheets therefore recommend a Kelvin (4-wire) connection, in which two heavy terminals carry the load current and two separate sense points measure the voltage directly at the resistor element. [Analog Devices](https://www.edgepedia.org/analog-devices)' AD8412A documentation reports that without a Kelvin connection, measuring on the top pad alone introduced about a 22.8% error, and that sense points should be placed at the outer extremity of the resistor.<sup>[6](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8412a.pdf)</sup>

## Construction and materials

Shunt resistors are built for two competing demands: a very low resistance that wastes little power, and a resistance value that stays constant as the part heats under that power. Manganin and other copper-manganese alloys are used for their low temperature coefficients; CTS's precision SMD shunts use a Cu-Mn resistance element for high thermal stability in energy meters, inverters, IGBT modules, and battery monitoring.<sup>[10](https://www.ctscorp.com/Products/Current-Sensors/Shunts)</sup> Large parts are made as metal strip or busbar elements, electron-beam welded, with inductance held below a few nanohenries so the reading stays accurate at high current slew rates.<sup>[11](https://www.bourns.com/docs/product-datasheets/csi2h-2512.pdf?sfvrsn=da6624f6_5)</sup>

Representative specifications show the spread of the component family:

- **Laboratory standards.** Ohm-Labs CS series precision shunts, rated 0.1 to 10 A at 1 V full scale, specify accuracy better than 0.005% to 0.01%, temperature coefficient below 5 ppm/°C, and AC/DC difference estimated below 0.01% to 1 kHz; each unit carries ISO 17025 accredited calibration through full rated current.<sup>[4](https://ohm-labs.com/precision-shunts/cs-1-10/)</sup>
- **Industrial power shunts.** Miba's PCS-100 M series operates at 100 W over 1 mΩ to 1 Ω with tolerances from ±10% down to ±1% and temperature coefficients of ±25 to ±150 ppm/°C, in a non-inductive design.<sup>[5](https://www.ebg-resistors.com/en/products/shunts)</sup>
- **Small-signal shunts.** Campbell Scientific's CURS100 data-logger module uses a 100 Ω bulk metal foil shunt with ±0.01% tolerance at 25 °C, a maximum temperature coefficient of ±0.8 ppm/°C, and a 0.25 W power rating, converting 4 to 20 mA sensor signals into a measurable voltage.<sup>[3](https://www.campbellsci.com/products/curs100)</sup>
- **Integrated shunts.** Texas Instruments' INA253 embeds a 2 mΩ Kelvin-connected precision shunt in the same package as its current-sense amplifier, with 4.5 mΩ total package resistance, continuous current handling up to 15 A under stated cooling conditions, and shunt drift as low as 25 ppm/°C even in the −40 °C to 0 °C range.<sup>[12](https://www.ti.com/lit/ds/symlink/ina253.pdf?ts=1778597679509)</sup>

## Self-heating and accuracy

Power dissipated in the shunt, \( P = I^{2} \cdot R \), raises its temperature, and any temperature coefficient then changes the resistance and the reading. Analog Devices' guidance is to select a shunt with a low temperature coefficient to minimize self-heating error and the resulting thermal nonlinearity.<sup>[6](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8412a.pdf)</sup> The same physics sets a safe current limit: the INA253's maximum continuous current is derated with ambient temperature, from 15 A at 85 °C to 10 A at 125 °C without forced airflow, and the shunt tolerates brief overcurrent excursions above the continuous limit without damage.<sup>[12](https://www.ti.com/lit/ds/symlink/ina253.pdf?ts=1778597679509)</sup> For the most demanding laboratory work, a 100 Ω RTD can be bonded directly to the shunt element so that resistance change with temperature can be characterized and compensated.<sup>[4](https://ohm-labs.com/precision-shunts/cs-1-10/)</sup>

## Applications

Shunt-based current measurement appears wherever a system must know how much current it is delivering or consuming. Documented uses include battery chargers and overcurrent protection, motor and solenoid control, power management in dc-to-dc converters and battery monitoring, telecom power amplifiers and base stations, and 4 to 20 mA industrial sensor loops read through a precision shunt.<sup>[9](https://www.ti.com/document-viewer/lit/html/SBOA165)</sup><sup> • </sup><sup>[13](https://www.analog.com/en/products/ad8217.html)</sup><sup> • </sup><sup>[3](https://www.campbellsci.com/products/curs100)</sup> In automotive and industrial power electronics, shunts serve in electric power steering, AC/DC converters, DC links, motor controls, starter generators, and charging systems.<sup>[10](https://www.ctscorp.com/Products/Current-Sensors/Shunts)</sup>

## References

1. [21.4 DC Voltmeters and Ammeters, College Physics, OpenStax](https://openstax.org/books/college-physics/pages/21-4-dc-voltmeters-and-ammeters)
2. [High Power Shunts, Bourns](https://bourns.com/products/resistors/high-power-shunts)
3. [CURS100 100 Ohm Current Shunt Terminal Input Module, Campbell Scientific](https://www.campbellsci.com/products/curs100)
4. [Precision Shunts, 0.1 to 10 Amp, Ohm-Labs, Inc.](https://ohm-labs.com/precision-shunts/cs-1-10/)
5. [Shunts, Ultra High Power Resistors, Miba EBG Resistors](https://www.ebg-resistors.com/en/products/shunts)
6. [AD8412A Datasheet, Analog Devices](https://www.analog.com/media/en/technical-documentation/data-sheets/ad8412a.pdf)
7. [High- vs. Low-Side Sensing, Technical Article SSZTA51, Texas Instruments](https://www.ti.com/document-viewer/lit/html/SSZTA51/GUID-8C507D4D-FB98-422A-AF78-D19B9067D75A)
8. [TIDA-00302 Current Shunt Monitor with Transient Robustness Reference Design, Texas Instruments](https://www.ti.com/tool/TIDA-00302)
9. [SBOA165: Low-Side and High-Side Current Sensing Basics, Texas Instruments](https://www.ti.com/document-viewer/lit/html/SBOA165)
10. [Shunts, Current Sensors, CTS Corporation](https://www.ctscorp.com/Products/Current-Sensors/Shunts)
11. [CSI2H-2512 Series Current Sense Resistor Datasheet, Bourns](https://www.bourns.com/docs/product-datasheets/csi2h-2512.pdf?sfvrsn=da6624f6_5)
12. [INA253 Current-Shunt Monitor with Integrated 2-mΩ Shunt Datasheet, Texas Instruments](https://www.ti.com/lit/ds/symlink/ina253.pdf?ts=1778597679509)
13. [AD8217 High-Side Current Shunt Amplifier, Analog Devices](https://www.analog.com/en/products/ad8217.html)

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*Topic: Encyclopedia › Technology and the built world › Engineering and manufacturing › Electrical and electronics engineering › Electronic components and devices*

*Initially written Sep 17, 2026 · Reviewed: Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*

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