Magneto-Elastic Resonance (MER) Sensors
At Acreo Sensor System we have developed read-out electronics and explored many application of magnetoelastic resonance (MER) sensors for more than 10 years. The principle is similar to the more well-known quartz crystal microbalance (QCM), but MER sensors are based on magnetoelasticity instead of piezoelectricity. A magnetoelastic material changes its dimensions when it is exposed to a magnetic field. A thin strip of a magnetoelastic material forms a resonator, similar to a tuning fork. Exposing the film to a short magnetic pulse excites the film and it starts to oscillate emitting a magnetic field. The frequency, amplitude and damping of the emitted magnetic field give information about the status of the sensor and the coating or media surrounding it. The main benefits of the sensor are:
- Wireless detection. The antenna to sensor range is a few decimeters in air and a few centimeters in a liquid.
- Passive sensor, meaning the sensor needs no battery or other power supply
- Low sensor cost. The sensor is made from a low-cost material, so it is well suited for applications where the sensor is disposed after use.
Applications and Sensor Systems
MERMAID is a compact instrument developed at Acreo Sensor Systems that use MER sensors to analyze liquid and thin-film properties. The MERMAID system can measure properties of a coating on the surface and of a medium surrounding the sensor. MER sensors, together with the MERMAID instrument, are useful in many applications, such as viscosity measurement, study of biofilm growth, food processing and lubricant testing and development.
An innovative design of the excitation and detection coil allows the instrument to be compact and portable. The wireless detection of the sensor allows the sensor to be placed a few centimeters away from the MERMAID instrument, which enables the sensor to be placed in a test chamber without any wires attached to the sensor.
Acreo Sensor Systems have developed a humidity detection system that uses inexpensive MER sensors wireless detection of relative humidity. The MER sensor is passive, so batteries or other power sources are not needed. With the reader, a MER sensor can be detected at a distance of a few decimeters. The wireless humidity detection system can be applied to measure humidity in places that are hard to reach, such as behind walls and in closed packages, and to monitor moisture in food, pulp and sand. We have conducted field tests of the system within many business areas, such as the automotive industry, the building industry and the personal-care industry.
For further information, please contact:
Peter Björkholm, Sensor systems
peter.bjorkholm [at] acreo.se