Electromagnetic sensors

XMR sensor operating at MHz sampling rates

© Fraunhofer ENAS
Sensor film with initial light intensity (left) and reduced intensity of sensor due to mechanical load (right).

Actual technical revolutions covering the IT sector, industry and our daily lives, pooled as internet of things, are accompanied with the development toward automatization and the capability for autonomous behavior. This trend is linked with the strong need for accurate, self-calibrating and reliable sensors, where magnetic field and current sensors are important classes supporting the advancements. Especially the latter is of importance for global efforts toward green energy and electromobility, too.

Fraunhofer ENAS, which has a long-term experiences with a variety of sensors and actuators together with their integration into smart systems, recently developed a technology demonstrator with an SPI interface, revealing a measurement data acquisition at MHz sampling rates shown by an example of a current sensor. As sensor, a high sensitive giant magnetoresistance (GMR) effect based Wheatstone bridge is used, enabling for sub-µT magnetic field resolution as well as ultra-high dynamic measurements of the magnetic stray field, which makes the measurement of, for instance, the amperage accessible. XMR sensors, which are always subject to saturation effects due to the ferromagnetic materials involved in the sensor layer stack, still can be used for broad range electric current sensors due to, e.g. a dedicated design of the XMR sensors, conductive paths or electromagnetic coils, to finally utilize the high sensitivity of this sensor class for current sensing. Another application example for XMR based magnetic field sensors, allowing for high frequency data acquisition, is the precise position determination and angular detection of rotational movements in, for instance, turbochargers.