Electronics key to unique magneto-inductive displacement sensor

Written by: Micro Epsilon UK Ltd | Published:

Micro-Epsilon's new mainSENSOR (Magneto-inductive) displacement measurement sensor combines eddy current sensor technology with the latest printed coil and permanent magnet technology. The sensor is therefore very compact relative to its measuring range and is very cost effective for mid-to-high volume OEM applications.

The magneto-inductive sensor was originally developed by Micro-Epsilon as a high volume, low cost solution for load detection in washing machines. Since then, the technology has been developed further, resulting in an industrial-grade family of standard displacement measurement sensors, which are ideal for mid-to-high volume OEM applications, including automotive, hydraulics, off-highway vehicles and special purpose machines.

Due to simplified electronics, Micro-Epsilon is now able to produce low cost versions of the sensor with printed circuit boards and basic analogue outputs, or can combine this version with a microprocessor to create a digital output sensor, including PWM, CANbus and other digital interfaces. The electronic circuit design and production is undertaken in-house at Micro-Epsilon's PCB production facility, allowing full design flexibility of the electronic layout combined with complete quality control over the product.

In contrast to the widely used Hall Effect measuring principle, mainSENSOR uses Micro-Epsilon's unique, patented measuring method, which is based on a linear relationship between the position of the permanent magnet and the output signal.

The underlying functioning principle of the sensor is based on a coil, which is supplied with alternating current, resulting in a primary magnetic field. According to the Maxwell formula, this magnetic field induces eddy currents in the electrically conductive material arranged opposite the coil. In the field of the eddy current sensor is a special film, which attenuates the eddy current sensor depending on the strength of the magnetic field. Using this method, a linear relationship between the distance to the magnet and the output signal can be established. As printed coils can be used inside the sensor, manufacturing does not rely on any semiconductor processes.

The sensor has an extremely high basic sensitivity, which enables a simple, low cost evaluation circuit. With an eddy current sensor as the core, both very fast and very high resolution versions of the sensor can be produced. A pulse width modulated signal is available as an output signal, which can be easily read by a microcontroller using a time measurement.

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