Absolute Rotor Position Sensors
Automotive Sensor Products
Absolute Angular Rotor Position Sensor
Features
Continuous rotary position detection
Power on position indication
Rotation speed and direction detection
Automotive AEC-Q100 grade 0 certified
Single and multiple pole pairs (capability to measure
angles within 360, 180, 120° ranges).
Can be a direct resolver replacement where sin/cos
signals are necessary.
Figure 1: Example of Rotor Position Sensor
Benefits
General Description
Contactless measurement – high robustness.
High accuracy (up to 0.2% full scale).
Intrinsic immunity to stray fields.
High tolerance to mechanical displacement and air
gap variation.
High reliability – no contacting parts.
Suitable for linear, arc and rotational applications.
The Absolute Rotor Position Sensor is an angular position
sensor measuring rotational angle of any rotary application,
such as motor position, steering wheel angle, etc.
The sensor assembly comprises two parts: sensor and
target. The sensor is stationary and fixed to the stator of the
motor or any appropriate stationary component in other
applications. The target is attached to a rotating part of the
application, e.g. rotor or shaft. The sensor measures the
angular target position and outputs the position signal(s).
Applications
Rotor position sensing of Brushless DC (BLDC) motors
Rotary position sensing up to 360°, e.g. steering angle
sensors
Small angle sensors; e.g. pedal, vehicle level, valve sensors.
Off-shaft or on-shaft implementations.
Operation
Basic Principle
The Littelfuse Absolute Rotor Position Sensor operates using the inductive eddy currents principle. The sensor contains at least 3
coils that are printed onto the Printed Circuit Board (PCB), At least one coil is an excitation coil, and at least 2 coils are reception
coils that are shifted by 90 degrees with respect to each other. The excitation coil is being fed by an AC voltage (sine shaped) in
frequency range of ~1-6 MHz. This voltage creates alternating magnetic fields in the coil which induces alternating currents in the
reception coils that have a phase difference of 90°.
A voltage is therefore generated in each of the reception loops, which is dependent on the current direction in each coil. The sum
of voltages in each loop is the output signal of the coil.
As the metal target approaches the coils, eddy currents are induced in the target metal layer. This creates opposing magnetic fields
to that of the coils, counteracting induced voltages in the respective loops that are adjacent to the target. As the target rotates above
the sensor PCB, the amplitude of the voltage output from the receiving coils exhibit sine and cosine profiles, creating a modulated
signal.
After demodulation and filtering, the sensor outputs sine and cosine signals that represent the rotary position of the target. This
signal can be directly fed to the vehicle ECU. Alternatively, the signal can be processed and outputted digitally.
Packaging Options
Custom packaging can be provided to meet any need, please contact Littelfuse Sales for details.
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