Magnetic Field Sensor Measures Forces in a Component

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When shafts and axles transmit large forces at high speeds, the bearings often suffer as a result. The material wears out resulting in abnormal or dangerous operating conditions. This is why system-critical components in industrial plants are constantly monitored. As well as measuring the transmitted forces, strain gauges mounted on the shafts also record mechanical changes in the material. Non-contact measurement using magnetic fields provides another option. To achieve this, Prof. Andreas Kolitsch and his team from Helmholtz-Zentrum Dresden-Rossendorf (HZDR) Innovation GmbH have developed HZDR's laboratory model into a practical sensor.

Using induction, the multifunctional Argus sensor can simultaneously measure eight mechanical operating variables such as speed, torque and position deviation. This enables the transmitted mechanical power or power surges to be displayed in real time. The measurement system consists of a large number of transmitter and receiver coils in a sensor head mounted a few millimetres from the shaft. The sensor's non-contact operating principle allows it to work in dusty, oily or chemically aggressive operating environments. Developer Dr. Dominique Buchenau explains the concept in simple terms: "When electrical current flows through a sensor's transmitter coil, a magnetic field builds up. The receiver coils detect this field. For example, when torsional forces or position deviations occur in the drive element during rotation, the receiver coils detect a characteristic change in the transmitter field, and we can evaluate this change."

Extending service intervals to save costs

"In practice, this measuring principle has already proven itself on the engine test bench of a Dresden-based company. The monitored shafts have a diameter of up to 50 centimetres in this case", says Kolitsch. However, the sensor can also be used for larger components and work is already underway on miniaturising the technology. The development team sees possible uses for the multifunctional sensor wherever shaft or axle failure is critical to the system, maintenance work is time-consuming or downtime is expensive. With continuous sensor monitoring, service intervals in offshore wind farms could be extended cost effectively and possibly without having to replace the drive elements according to a fixed schedule. For heavy drilling equipment or industrial grinders, the sensors can sound the alarm if the system deviates from a set operating parameter range. In this case, a rapid shutdown would prevent system-critical overloading of the electromechanical components. In future, the sensor could also be used in other areas such as the automotive industry.