Current Sensor
Reports the current through a conductor as either an analog voltage (proportional to current) or a digital value over I²C/SPI. Hall and fluxgate types are galvanically isolated from the measured current.
Shunt: measure the millivolt drop across a precision resistor with a current-sense amplifier. Hall: measure the magnetic field around the conductor with a Hall element. Fluxgate / closed-loop: null the field with a feedback coil for high-accuracy DC measurement.
In plain terms
Some current sensors are like a doctor taking your pulse without touching skin (Hall, magnetic — non-contact). Others are like reading a flow meter inline (shunt — small in-circuit drop).
Why designers use it
- Battery state-of-charge integration (coulomb counting).
- Motor-control current loops in BLDC and stepper drives.
- Overcurrent protection trips in power supplies.
- Mains energy metering (revenue-grade, certified).
Best for
- Battery monitoring
- Motor control
- Power metering
Key specifications
- Operating limits: Check the exact manufacturer's datasheet (A family name does not establish voltage, current, temperature or timing limits.)
- Pin assignment: Match the complete part and package code (A similar name or function does not guarantee the same wiring.)
- Mechanical fit: Use the exact package drawing (Check pad layout, dimensions and viewing direction before building.)
When not to use it
- Sub-µA leakage currents — shunt-amplifier noise floor is in the µA range; use a transimpedance amp instead.
- When isolation matters and you can't afford a Hall/fluxgate — shunts share the current path's potential.
Common mistakes
- Routing the shunt sense traces as long single-ended runs and picking up noise — use Kelvin sensing.
- Forgetting that Hall sensors drift with temperature and need offset calibration.
Where you will find it
- Tesla and other EVs use closed-loop fluxgate sensors for ±0.1 % battery-current accuracy.
- Smart meters use either a shunt + isolated ADC or a current transformer for revenue-grade measurement.
- Drone ESCs use a shunt + INA-class amplifier for phase-current sensing.
A short history
The Hall effect was discovered by Edwin Hall in 1879. Hall-effect current sensors became practical in the 1980s with integrated bias circuitry; closed-loop fluxgate sensors (LEM, VAC) emerged from instrumentation work in the 1970s.