Magnetic Sensor Technology
This page explains magnetic sensor technology used in S-cube products.
Used in AK0991x / AK0997x series
A Hall element is a device that uses the Hall effect. “Hall” came from Dr. Hall's name for discovering Hall effect. It is based on the phenomenon that the electromotive force appears in the direction orthogonal to both the current and the magnetic field when applying a magnetic field perpendicular to the current to the object through which current is flowing.
When a current is applied to a thin film semiconductor, a voltage corresponding to the magnetic flux density and its direction is output by the Hall effect. The Hall effect is used to detect a magnetic field, (shown in Figure 1).
Hall elements can detect a magnetic field even in the case of a static magnetic field with no change in magnetic flux density. Therefore, Hall elements are used in various applications, such as non-contact switches used in combination with magnets, angle sensors, and current sensors. Geomagnetic sensors using Hall elements are widely used in smartphones and other applications.
An element that detects a magnetic field using a material, that resistance changes when magnetic force is applied, is called a magnetoresistive, (MR), element.
Other than semiconductor magnetoresistive element, (SMR), there are three kinds of sensors as representative examples of the magnetoresistive element using a ferromagnetic thin film material such as anisotropic magnetoresistive element, (AMR), giant magnetoresistive element, (GMR), and tunnel magnetoresistive element, (TMR).
◆Tunnel Magnetoresistive Element (TMR)
Used in AK0994x series
In the case of a laminated film of ferromagnetic material, (pinned layer), insulator and ferromagnetic material, (free layer), the proportion of electrons passing through the insulator changes due to the tunnel effect and the resistance value changes depending on if the direction of magnetization of the pinned layer and the free layer are antiparallel (a) or parallel (b).
Tri-axis magnetic sensor
Magnetic fields of various magnitudes exist in the world. There are no products that can comprehensively measure magnetic fields of all magnitudes with a single sensor. The type of sensor depends not only on the magnitude of magnetic field to be measured, but also on applications. AKM has a lineup of three S-cube products that fit the size of magnetic field to be measured.
The AK0997x series is the most suitable sensor for measuring the large magnetic fields in milli-tesla range, such as those produced by magnets.
They have a wide measurement range and is designed to be difficult to overflow even when the magnet is installed close to the sensor. therefore, it is suitable for applications (e.g., opening and closing detection applications) to be used together with the magnet.
The AK0991x series is the most suitable sensors for measuring small magnetic fields in the micro-tesla range, such as geomagnetism.
They are used as electronic compasses for heading-up applications in map application such as smartphones.
The AK0994x series is the most suitable sensor for measuring the minimum magnetic field in the nano-tesla range.
We believe that it can also detect very small magnetic fields, such as those generated by weak magnetic materials and the Villari phenomenon (reverse magnetostriction effect) and can therefore be used in application such as torque sensors and micro-metal strip detection.