Hello.
Today we're demonstrating linear sensing with NVE's brand new AET-Series linear position
and off-axis rotational sensors
Here's how it works; Linear magnetic scale, or linear magnetic tape, is a special type
of magnet that has alternating north and south poles molded into a thin strip, often backed
with adhesive
This arrangement produces a strong magnetic field on one side of the tape and zero field
on the other
The magnetic poles repeat periodically with a precision tolerance spacing known as the
"pole pitch."
NVE's new AET-Series TMR sensors have phase shifted linear elements.
When the pole pitch matches the phase shift, the sensor produces high amplitude sine and
cosine outputs for position interpolation.
The AET-Series has several sensors optimized for many of the most common pole pitches.
Today we're using the AET500-02E with a five- millimeter linear magnetic scale.
Here's the demo board.
And here's the magnetic tape with Gauss paper to show the location of the poles.
The AET500 fits in an eight-pin SOIC, which is amazing for a five-millimeter scale sensor.
We're displaying the repeating position along the tape with a micron resolution display
controlled by an ATtiny85 microcontroller.
We have one red and one yellow LED to indicate pole position. Since this is a precision demonstration,
we're using an inexpensive dual CMOS op-amp to boost signals to full scale.
AET-Series sensors have a high output, so we only need a gain of three in this circuit
We'll slide the tape under the mounting fixture, and turn the power on--and the sensor reads
the position along the zero to five millimeter segment to micron precision.
The meter counts 1 to 5000.
As we move along the tape, the red LED brightens proportionally to distance, reaching maximum
brightness when a pole is detected, and the yellow LED flashes when the sensor is within
one human hair of a pole.
The resolution is simply amazing!
In this demo, we needed to use our largest pole pitch sensor for the tape position to
be reasonably controllable by human touch at all.
And when we take our hands off the tape, the meter keeps a steady reading, showing how
low noise and high precision these sensors really are.
Here's the circuit.
The sensor has half-bridge sine and cosine outputs, and we boost them to full scale with
a noninverting amplifier configuration.
The microcontroller calculates the position with an arctangent function and interfaces
to a seven-segment display via I2C.
LEDs indicate the pole position
The firmware is simple.
We read the sensor and calculate the position along the five millimeter scale by converting
the angle to microns.
We output the position on the display and the indicator LEDs.
Key features for NVE's AET-Series Linear Positioning and Off-Axis Rotational sensors include:
Low hysteresis and excellent linearity for high accuracy.
Robust airgap for mechanical latitude.
Ultraminiature packages for the most space-constrained systems.
And micron precision due to the sensor's low noise and high sensitivity.
Design support for AET-Series sensors can be found on our applications page:
Click, email, or call for more information, or to buy NVE sensors today.