How does a magnetic current sensor work?

Magnetic current sensing plays a role, in industries such, as automotive, industrial and personal electronics. It enables the invasive assessment of electric currents by leveraging Amperes Law and the magnetic field produced by current carrying conductors. In this detailed article we will delve into the mechanisms of current sensors the diverse technologies employed and their practical uses.

Direct Vs. Indirect Sensing

When it comes to detecting current there are two methods; sensing and indirect sensing. Direct current sensing involves using Ohms Law and placing a shunt resistor, in line with the load to measure the voltage drop, across it. This approach is considered invasive since the sensing circuitry is physically connected to the system under observation.

On the hand indirect current sensing, also referred to as current sensing is based on Amperes Law. According to this law the magnetic field surrounding a conductor is directly related to the current flowing through it. Magnetic current sensors detect the field produced by the conductor carrying current without requiring a direct electrical link.

Ampere's Law and Magnetic Field

Ampere’s Law plays a role, in electromagnetism by connecting the field surrounding a closed loop to the electric current flowing through it. It explains that the strength of the field is directly linked to the amount of current enclosed within the loop. This correlation enables sensors to indirectly measure current by detecting changes in the magnetic field.

To determine the orientation of field lines individuals often rely on the right hand rule. By pointing your hands thumb in the direction of flow your fingers naturally follow the path of magnetic field lines around a conductor. Understanding this aspect is critical for current sensors as they rely on a specific axis, for accurate sensitivity.

Magnetic Current Sensing Technologies

There are various magnetic current sensing technologies have been developed, each, with its mechanical and magnetic integration. These technologies encompass module based sensing, ambient magnetic current sensing and, in package magnetic current sensing.

  1. Module-Based Sensing: The use of module based sensing entails utilizing a toroid or a similar geometric shape to focus the field produced by the conductor carrying current. Such setups are usually supplied by manufacturers. Demand intricate magnetic planning.
  2. Ambient Magnetic Current Sensing: Ambient magnetic current sensing makes use of the field naturally present, around a PCB trace, bus bar or any other conductor to measure the flow. Linear hall sensors or similar magnetic sensors are positioned at a distance from the conductor to pick up on the field. Magnetic concentrators or shields might be used to boost signal strength or reduce interference, from fields.
  3. In-Package Magnetic Current Sensing: In package magnetic current sensing is an innovation that involves the passing through the device package. An isolated sensor IC internally measures the field produced by the current flowing through the lead frame. This technology is well suited for handling currents on a PCB. Provides built in galvanic isolation.

Advancements in Magnetic Current Sensing

In the past magnetic current detection was mainly used for needs typically exceeding 100 amps. The sensors were quite pricey. Required considerations, in magnetic design. However technological progress has paved the way for the creation of cost effective devices like, in package magnetic current sensors.

These sensors enclosed in packages are well suited for currents. Can be seamlessly integrated into PCB designs. They offer performance, reduced power consumption and built in galvanic isolation. These improvements have expanded the possibilities of using detection across a wider array of applications.

Understanding Ampere's Law and the Right Hand Rule

Amperes Law, as previously mentioned is a concept, in the field of electromagnetism that links the field to the electric current flowing through a conductor. By following the right hand rule we can determine the orientation of the magnetic field lines surrounding the conductor.

To apply the right hand rule forms a thumb up gesture with your hand. Align your thumb in the direction of the current flow. The curling of your fingers will indicate the path of the field lines. This rule plays a role, in comprehending how magnetic current sensors identify and gauge fields.                                                                 

Axis of Sensitivity in Magnetic Current Sensors

Magnetic current sensors are designed with a sensitivity axis that dictates the direction in which they can detect fields. Typically these sensors are most responsive, to fields that run perpendicular to their packaging. This means that if the magnetic flux does not align with their sensitivity axis they will not register any output.

For example if a magnetic current sensor is placed above a PCB trace it may not pick up the field since it is moving parallel to the package rather, than into it. To ensure readings it is important to position the sensor beside the trace where the field enters the packaging.

Implementations of Magnetic Current Sensing

Various technologies can be implemented for sensing all rooted in the fundamental principles outlined by Amperes Law. The key distinction, among these approaches lies in how they integrate magnetic elements well as in the positioning of the magnetic field in relation to the current flow.

One method involves module based sensing, which employs toroids or other shapes to concentrate the field produced by the current carrying conductor. These systems necessitate design and are commonly sourced from external manufacturers.

Conversely ambient magnetic current sensing capitalizes on the field generated by the conductor itself. Linear hall sensors or similar devices are stationed at a fixed distance from the conductor to gauge this field. Magnetic concentrators or shields might be employed to amplify signal strength or mitigate fields influence.

In package magnetic current sensing represents a innovation where the current passes through the device package itself. The internal sensor IC measures the field created by flow through the lead frame. This technology boasts isolation and is particularly suitable for lower currents, on a printed circuit board (PCB).

Applications of Magnetic Current Sensors

Magnetic current sensors are used in industries and systems that need dependable current measurements. They have a range of applications including;

  • Automotive: Magnetic current sensors are used in electric and hybrid vehicles for motor control, battery management, and charging systems.
  • Industrial: They are employed in motor control systems, power inverters, robotics, and renewable energy systems.
  • Personal Electronics: Magnetic current sensors are used in smartphones, tablets, laptops, and wearable devices for battery management and charging control.
  • Smart Home: They find applications in smart lighting, HVAC systems, energy monitoring, and power management.
  • Industrial Automation: Magnetic current sensors are used in control systems, motor drives, and power monitoring in industrial automation applications.

These are just a few examples, and the versatility of magnetic current sensors allows for their integration into various other systems and applications.


Magnetic current sensors are vital, for measuring currents without the need for direct electrical connections. By using Amperes Law and the right hand rule these sensors. Measure the field created by current carrying conductors. Technological progress has made magnetic current sensing more affordable and accessible allowing its integration into applications across industries.

Whether in settings or personal electronics magnetic current sensors offer dependable and precise current measurements. AKM provides customers with support and access to the advancements in current sensing technology leveraging their expertise in the field. As technology advances magnetic current sensors will undoubtedly play a role, in shaping our interconnected world.

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