Inductive sensors suit automotive applications

Optek Technology has developed a versatile inductive sensor technology that can be used for a wide range of automotive and vehicle applications.

Giving automotive electronics design engineers a new noncontacting precision position sensor that provides absolute position as well as 360-degree angle and linear displacement sensing, TT Electronics Optek Technology has developed a versatile inductive sensor technology that can be used for a wide range of automotive and vehicle applications.

Designated as Autopad technology, the patented sensor consists of a moveable "puck", which interacts with a fixed "pad" containing a series of transmit and receive coils, which generate a specific magnetic field.

The puck's movement varies the phase of the magnetic field and thus can be used to determine absolute position.

"Our Autopad technology produces an extremely rugged position sensor that is virtually immune to temperature, vibration, and other environmental factors that can interfere with other types of sensors", said Dale Teeters, Director of Optek Technology's Automotive Business Unit.

"The sensor is also remarkably tolerant to misalignment, particularly in the z-axis direction".

In a typical automotive application, the Autopad sensor pad would contain a series of transmission coils (sine or cosine patterns embedded in a PC board, or printed conductors or actual coil windings), as well as a "receive" coil (usually an aerial loop around the perimeter of the pad).

The "puck", or moving part of the sensor, is typically a small disc that interacts with the transmission and reception coils to change the phase of the magnetic field generated by the pad.

Multiple pucks can be detected in relation to a single pad.

These phase change signals are processed by an external electronics assembly that is used to measure the position of the puck in relation to the pad, and thus determine absolute position along the x, y or z axis; 360-degree angle sensing, as well as linear position sensing along a straight or curved surface, depending on the geometries chosen for the pad design.

The electronics assembly is customer and application specific, and can be implemented with discrete components; an ASIC solution will be available in 2006 for higher volume standard applications.

The Autopad technology achieves linearity performance of better than 1%, with 0.1% resolution (at 10bit), and an input/output rate of 1kHz.

The sensor's output is analogue (ratiometric) or pulsewidth modulated (PWM); other standard automotive bus protocol interfaces are also planned.

Automotive applications for Autopad technology include chassis height sensors, headlamp leveling, ride height and suspension control systems, pedal and steering sensors, throttle position sensors, gearbox and transfer case sensing systems for standard and automatic transmissions; as well as vehicle-driver interfaces, such as panel controls, switches and mirror or seat position adjustment systems.

Pricing for the Autopad sensor technology will be determined by each application's requirements (as a custom sensor).

Lead times can be estimated on an individual basis after prototype development per customer.

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