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Off-Axis
Angle Sensing |
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NVE TMR angle sensors are used in a variety of applications including encoders,
robotics, motor controls, and automotive applications. But what happens when you
can’t center the magnet over the sensor?
Fortunately, these sensors are especially robust in off-axis configurations. There
are two off-axis configurations: parallel-plane off-axis or perpendicular-plane
off-axis.
Parallel-Plane Off-Axis
The parallel-plane off-axis configuration often uses a diametrically-magnetized
ring magnet mounted on a shaft. The angle sensor is displaced vertically and radially
to detect the rotating field:
Sensor out-of-plane with a ring magnet with the sensor plane and magnet planes
parallel. Distances are measured center-to-center.
For the best accuracy, the sensor should be placed where the rotating magnetic
flux is a constant magnitude. This is achieved by choosing R0 and z0 so that:
Perpendicular-Plane Off-Axis
The configuration with the magnet plane perpendicular to the plane of the sensor
is shown below:
The second off-axis configuration, with the sensor plane perpendicular to the
magnet plane. The plane of the sensor should be tangential to the blue circle,
as shown.
Accuracy in this configuration is optimized at one of two locations:
A Web App
To make these calculations easy, we have a free Web
application to calculate the ideal spacings for both off-axis configurations
and any size magnet.
The Sensitivity Advantage
The magnetic field for off-axis geometries is significantly smaller than on-axis,
which requires sensitive sensors. NVE offers high accuracy angle sensors that
operate in as little as 1.5 mT, significantly less than other technologies. Our
high-sensitivity sensors make off-axis angle sensing possible with small, inexpensive
magnets.
Live Demonstration
Here’s an off-axis angle sensing live demonstration:
A Range of Angle Sensors
NVE offers a range of TMR
angle sensors including analog
angle sensors, and
Smart Angle Sensors, which include integrated digital signal processing
and SPI interfaces. All of our angle sensors offer a unique combination of speed
and accuracy.
More Information:
Application
Note (.pdf) »
Off-Axis Angle-Sensing
Web App »
TMR
Angle Sensors »
Smart
Angle Sensor Demo Board »
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Upcoming
Exhibitions |
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 NVE
distributor K.K. Rocky will be exhibiting sensors, isolators, and the popular
smart-sensor based xylophone at Embedded Technology & IoT Technology,
November 20 to 22 in Yokohama, Japan. |
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