Monitoring of bolted joints – wireless, self-powered and retrofittable

Bolted connections are often used in critical, safety-relevant places such as bridges, wind turbines, vehicles or machines, where they are permanently exposed to high loads. To ensure the safety of these connections, they require permanent monitoring of the preload force.

Q-Bo® measures precisely and transmits wirelessly

The smart screw connection Q-Bo® enables wireless, self-powered monitoring of the preload force with the aid of a retrofittable sensor system: Using a special pressure and temperature thin film, known as the DiaForce® film, the tightening force as well as the temperature of the screw connection is regularly determined at the assembly location and transmitted to a cloud via a standardized interface.

Distribution of the preload force on the sensor disk
© Fraunhofer IIS
Distribution of the preload force on the sensor disk

The standardized mioty® radio technology is used to transmit the data, which is characterized by high energy efficiency and robustness over long distances.

The energy supply for the sensor and radio system is ensured by energy conversion from the immediate environment (energy harvesting). The smart screw connection Q-Bo® contains a thermogenerator that converts the smallest temperature gradients at the screw head into electrical energy and thus operates the sensor self-sufficiently. Alternatively, the sensor and radio can also be powered by a solar cell or a small battery.

The smart screw connection Q-Bo® enables precise measurement of the preload force during assembly and operation. Deviations can thus be detected immediately via remote maintenance and downtime or maintenance times can be avoided – a complete control of critical bolted joints.


  • Low energy consumption
  • Range of several kilometers
  • High robustness in difficult environments


  • Self-powered operation through energy harvesting
  • Integrated energy storage for constant transmission of acquired sensor data


  • Use of DIN screws
  • Can be retrofitted to existing screw and clamp connections

How does the smart screw connection Q-Bo® work?

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The smart screw connection Q-Bo® is a fully integrated IoT device with energy self-powered and wireless data transmission.

Find out more about the smart screw connection Q-Bo®, in which an integrated thin-film sensor system detects minimal changes in the preload force, transmits them wirelessly to a control unit and thus registers early detection of the loosening of a screw connection - wherever critical screw connections are used.  

Application Areas


Permanent monitoring

Wind power plants

Forward planning


Ensuring safety


Efficient work

Flange connections

Monitoring of tightness


Avoidance of downtime

Peter Spies

Contact Press / Media

Dr.-Ing. Peter Spies

Project Manager

Fraunhofer CCIT
Nordostpark 84
90411 Nuremberg, Germany

Phone +49 911 58061-3310

Philipp Schwerna

Contact Press / Media

Dr.-Ing. Philipp Schwerna

Business Development

Fraunhofer CCIT
Nordostpark 84
90411 Nuremberg, Germany

Phone +49 911 58061-6434

*Q-Bo® is a registered trademark in Germany