Detection methods can be roughly divided into the following.
- Open/close and position detection: Distance between the magnet and AMR sensor changes (Strength of magnetic force lines)
- Rotation detection: Direction of magnet changes (Direction of magnetic force lines)
For suitable AMR sensor candidates based on the positional relationship with the AMR sensor and movement of the magnet, see the Selection Guide. From these candidates, select the supply voltage, response frequency (high frequency type for magnets with quick movements), and current consumption (low current consumption type for battery driving).
(2) Use the Simulation Tool to determine whether the sensor turns on and off based on the positional relationship with the AMR sensor and magnet.
Although the Simulation Tool cannot cover all operation patterns, it can provide a simplified estimate of the ON/OFF level based on the positional relationship between the AMR sensor and any rectangular magnet.
(In the Simulation Tool, the position is an estimate only. Be sure to always check in the actual device.)
The detection directions of magnetic fields are different.
In a Hall effect sensor, when the magnet is directly above the sensor, the axis between the north and south poles of the magnet is perpendicular to the sensor. In an AMR, it is parallel to the sensor.
Because the magnetic force is strong near the north and south poles of the magnet, when credit card or other magnetic data is near, it could affect the card data. And so, AMR sensors are advantageous when the magnet will not be placed perpendicularly in electronic devices such as smartphones and notebook PCs.
(This does not mean that magnetic data is not lost when a horizontal placement is used.)
When the magnet position cannot be changed significantly, the AMR sensor can be turned off by the direction of the magnetic force lines. This can be used for applications in switches with extremely short strokes and in rotation detection.
What are the key points in distinguishing AMR sensors from reed switches?
Reed switches have mechanical contacts, and so the contacts have a limited lifespan, and they are sensitive to impact and vibrations.
(Have you ever had reed switches that failed to work after product delivery? They may have been affected by a strong impact during transportation or when mounting.)
AMR sensors have a higher impact durability than reed switches, have a smaller size, and when the magnet position cannot be changed significantly, the AMR sensor can be turned off by the direction of the magnetic force lines.
This can be used for applications in switches with extremely short strokes and in rotation detection. Also, because the magnetic field detection direction is the same as reed switches, magnets that were used in reed switches may be able to be used without modification in AMR sensors in some cases.