WEBVTT

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Welcome to the NVE
Sensor Design Corner.

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A customer asked how they could sense
15 mm of linear motion

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from 5 to 10 millimeters off axis.

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We're recommending a magnetic angle sensor.

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That's right--an angle sensor.

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The sensor detects the field
in two perpendicular axes,

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and calculates the angle
of the field between the axes.

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In this configuration,

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the angle is roughly proportional
to the linear displacement.

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To test it out, we connected an angle sensor
evaluation board to an Arduino.

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A linear stepper moves the magnet.

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We're using multiple
5 mm-diameter, 2.5 mm-thick magnets

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so we can show the tradeoffs
between magnet length,

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output range, and linearity.

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We'll start with two magnets
for 5 millimeters of magnet length.

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The angle range is large.

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The sensor resolution is a tenth of a degree,

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so the linear resolution is about
eight microns over 15 mm of travel,

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although with a fair amount of nonlinearity.

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If need be, we can calibrate the sensor
to correct the nonlinearity.

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More on that in another video.

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Next, a 10 mm magnet.

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The output range decreases slightly

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but the linearity improves.

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Finally, a 15 mm magnet.

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The resolution decreases a bit more
and the linearity improves further.

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The customer was going to use
a 10 mm magnet as a reasonable tradeoff

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between resolution and linearity.

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As you'd expect,
a 10 mm magnet has the same characteristics

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as the four 2.5 mm magnets we tested.

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Here's the Arduino program.

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We can read the sensor
with a single line of code.

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The program sends the data
to a terminal monitor.

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CoolTerm terminal monitor plots the data.

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CoolTerm also scales the graph to degrees,

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since the sensor output
is in tenths of a degree.

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So we've seen how a magnetic angle sensor

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can be used to accurately measure
linear displacement.

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Here's a link to the evaluation board we used.

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Click, e-mail, or call us
for more information.