Geomagnetic Sensor
Application note
2012/09/04
Page 1/7
Alps Magnetic Encoder
Sensor device
Application Note
www.alps.co.jp
Geomagnetic Sensor
Application note
2012/09/04
Page 2/7
-CONTENTS1.
2.
3.
4.
5.
Basic Information about ALPS GMR Magnetic encoder ........................................ 3
Design Guide ................................................................................................................. 4
Magnet and sensor layout ........................................................................................... 5
Evaluation equipment .................................................................................................. 6
Legal Disclaimer............................................................................................................ 7
Magnet for encoder
Detect rotation speed and direction
Design guide
Magnet size and magnetic field
Sensor to Magnet distance
Sampling rate/Max speed
Temp dependency
Application circuit
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Geomagnetic Sensor
Application note
2012/09/04
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1. Basic Information about ALPS
GMR Magnetic encoder
GMR sensor can detect this Br and B Φ
There is magnetic field distribution beside the
element individually.
magnet.
There are two GMR sensor elements inside ALPS
If the magnet rotates, field distribution also changes.
sensor device package,
Magnetic sensor device can detect this field
One element detects Br field,
distribution change.
And another element detects BΦ field.
Combined ASIC process these GMR signal and
output 2-phase Hi/Lo signal.
Then sensor can detect magnet rotation speed and
direction.
Magnetic field is from magnet N-pole to S-pole.
ALPS GMR sensor can detect this magnetic field
direction change.
Magnetic field has two elements,
One is Br element : radius direction.
Another is BΦ : Φdirection.
Br and B Φ
element strength is changing
alternatively with 90 degree phase offset.
2. Design guide
Device structure
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Geomagnetic Sensor
Application note
2012/09/04
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Definition of Br-Sensor, BΦ-Sensor
Sensor device is consisted from two GMR element
and electrical circuit.
Br and BΦ two direction sensors are combined
Br GMR element output is related to OUT1 , and BΦ
in one package device.
GMR element is related to OUT2.
Two sensor sensitivity direction is 90degre different,
So OUT1 and OUT2 has 90degree phase difference
with any pole pitch magnet.
Br and BΦ sensing area center is located as below
picture. Br and BΦ sensitivity center is at same
position.
Br and BΦsensor output is processed in IC circuit
with amplifier and comparator, then final OUTPUT
signal becomes Hi/Lo signal.
3. Magnet and Sensor layout
2.1. Definition of Br ,and BΦ-Sensor
There are some recommendations for Magnet and
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Geomagnetic Sensor
Application note
2012/09/04
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sensor layout.
1.Radial magnet /
Sensor is located beside the magnet.
・Sensor can detect magnet rotation at any layout.
・Setting the sensor on the line of Magnet Edge is
recommended for accurate 2-phase sensing.
2. Radial Magnet /
Sensor is located vertical to magnet.
・3.1 Magnet recommendation
Any type magnet can be used.
Magnetic field strength should be more than 1.5mT,
(more than 3mT is recommended for accurate
sensing.)
In the case of Ferrite-Magnet,
Magnet surface to sensor top Gap capability is
similar value to magnet pole pitch.
4. Evaluation equipment.
3.Axial Magnet /
Sensor is is located under the magnet.
・Sensor sample can be delivered as package device
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Geomagnetic Sensor
Application note
2012/09/04
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alone or Test PCB mounted style like below.
・Sensor can be evaluated with magnet and power
supply.
Environmental
chamber
or
Hermhorz
coil
equipment is useful.
・Oscilloscope can measure OUT1 and OUT2 signal.
・4.1. Recommendation circuit
5. Legal Disclaimer
Sensor device is using CMOS IC,
Bi-pass capacitance is strongly recommended.
THIS
INFORMATION
ON
THE
NOTE
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Geomagnetic Sensor
Application note
2012/09/04
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("INFORMATION") SHOULD BE USED ONLY AS A
GUIDE.
ALPS MAKES, AND YOU RECEIVE, NO
WARRANTIES
OR
CONDITION,
EXPRESS,
IMPLIED, STATUTORY, OR OTHERWISE, AND
ALPS SPECIFICALLY DISCLAIMS ANY IMPLIED
WARRANTIES
OF
MERCHANTABILITY,
NON-INFRINGEMENT AND FITNESS FOR A
PARTICULAR PURPOSE.
ALPS DOES NOT WARRANT THAT THE USE
OF
THIS
INFORMATION
WILL
BE
UNINTERRUPTED OR ERROR FREE OR THAT
THIS
INFORMATION
WILL
MEET
YOUR
REQUIREMENTS.
THE USE OF THIS INFORMATION IS
ENTIRELY AT YOUR RISK
IN NO EVENT WILL ALPS BE LIABLE FOR
SPECIAL,
INDIRECT,
INCIDENTAL,
WILLFUL,
PUNITIVE,
EXEMPLARY,
OR
CONSEQUENTIAL DAMAGES, DAMAGES FOR
LOSS OF BUSINESS PROFITS, OR DAMAGES
FOR LOSS OF BUSINESS
OR ANY THIRD
PARTY ARISING OUT OF THE USE OF THIS
INFORMATION , INCLUDING BUT NOT LIMITED
TO THOSE RESULTING FROM DEFECTS IN THE
INFORMATION, OR LOSS OR INACCURACY OF
DATA OF ANY KIND, WHETHER BASED ON
CONTRACT, TORT OR ANY OTHER LEGAL
THEORY, EVEN IF ALPS HAS BEEN ADVISED OF
THE POSSIBILITY OF SUCH DAMAGES.
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