How Does A Shunt Resistor Work
What Is a Shunt Resistor?
A shunt resistor (also called a current shunt) is a precision, low-resistance component used to measure electric current. It works by converting the current flowing through it into a small, measurable voltage drop — following Ohm’s Law (V = I × R).
How It Works — Step by Step
A shunt resistor, also known as a current shunt, is one of the simplest yet most reliable components used for current measurement in electrical and electronic systems. Whether it’s monitoring battery performance, tracking energy usage, or protecting sensitive circuits, the shunt resistor plays a vital role behind the scenes.
Current Flow
The shunt resistor is connected in parallel or series with the load (usually in series for current sensing).
When current flows through the resistor, a tiny voltage drop appears across its terminals.
Voltage Drop Measurement
Because the resistor has a very low resistance value (typically in the range of micro-ohms to milliohms), the voltage drop is minimal and doesn’t significantly affect the circuit.
Conversion to Current Value
Using the measured voltage (V) and the known resistance (R), the actual current (I) can be calculated:
This signal is then sent to an amplifier, ADC, or microcontroller for processing or display.
Example
If a shunt resistor of 0.001 Ω (1 milliohm) has a voltage drop of 50 mV,
then the current through it is:
Where It’s Used
- Battery Management Systems (BMS) – monitor charge/discharge current
- Power Supplies – detect load current
- Electric Vehicles (EVs) – measure motor or battery current
- Industrial Equipment – monitor energy consumption
Key Advantages
- High accuracy and linearity
- Simple and cost-effective
- Works for both AC and DC current
- Excellent temperature stability (when made from metal alloys like MnCu or NiCr)