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Draw-wire displacement sensors from Micro-Epsilon are playing an important role in testing the latest generation of wind turbine blades at the Fraunhofer Institute in Bremerhaven, Germany.

The test rig at the Fraunhofer Institute simulates the distortion of rotor blades due to the effects of wind forces.

The tip of the rotor blade can be distorted by up to 10m due to mechanical loads.

The rig is designed to measure rotor blades at a length of up to 70m.

During tests, the rotor blade is mounted horizontally in the test rig.

Steel cables are attached to the rotor using guide pulleys and fixed to the rotor blade at various positions along its length, either directly or via mechanical clamps.

Twelve draw-wire sensors from Micro-Epsilon are used to measure the distortion.

Two draw-wire sensors for each cable are mounted to the rails on the floor.

These sensors measure the movement and the distortion of the rotor blade.

The P115 sensors are from the company’s Wiresensor range and have measuring ranges of between 3m and 10m.

The sensors operate with a digital output signal and have an aluminium housing.

The principle of a draw-wire displacement sensor is relatively straightforward, hence its inherent reliability.

A draw-wire sensor works like a tape measure, except that the user does not have to read off the measurement of the extended tape.

The rotation of the drum on which the steel wire is wound is measured automatically.

The drum incorporates a long-life spring drive, which ensures that the steel wire is rewound.

’In addition to wind turbine testing, our draw-wire sensors are being used in a wide range of applications, from general industrial machinery and scissor lifts, through to more specific uses such as dentist chairs, patient lifting tables, theatre stages, pneumatic and hydraulic systems, aircraft landing gear and forklift trucks,’ said Chris Jones, managing director at Micro-Epsilon (UK).

The Wiresensor range uses three main measurement methods: a multi-turn potentiometer, an incremental encoder or an absolute encoder.

One of these devices is mounted onto the drum axle, converting the rotary motion of the drum into a signal that can be evaluated.

The measured displacement can be output as an analogue current, voltage or potentiometric signal.

For a digital output, there is a choice of HTL or TTL, with interfaces for most of the common fieldbus systems, including CANopen, SSI and Profibus.

As with traditional tape measures, the Wiresensor series is capable of measuring around corners and edges.

Micro-Epsilon supplies deflection pulleys, which deflect the steel wire in the desired direction.


With over 45 years experience and more than 15,000 customers worldwide, Micro-Epsilon understands the need for accurate, robust, intelligent sensors and measurement systems.

With over 45 years experience and more than 15,000 customers worldwide, Micro-Epsilon understands the need for accurate, robust, intelligent sensors and measurement systems.

If you are measuring any type of displacement / position, temperature, speed or colour parameters, Micro-Epsilon sensors and systems provide market-leading performance, together with the fastest measuring rates, highest operating temperature ranges and smart interface capabilities. From simple, low cost sensors to high volume, customer-specific OEM solutions, Micro-Epsilon will have athe correct measurement solution for your application.

Using both contact and non-contact measurement techniques, Micro-Epsilon boasts one of the largest ranges of displacement sensors including 1D, 2D & 3D laser optical, confocal chromatic, eddy current, capacitive, inductive, draw-wire and time-of-flight technologies. Measuring ranges are from nanometers to kilometers!

For temperature measurement, there is a comprehensive range of non-contact infrared temperature sensors and thermal imaging cameras capable of measuring up to that include intelligent software packages to support configuration, analysis and management during the application. LED analysers, fibre optic sensors and Colour recognition sensors measure true colour using L*A*B and CIE.

Micro-Epsilon sensors are used throughout almost all industries: from automotive to aerospace, motorsport to metal production, semiconductor to subsea. Whether it’s an R&D, test, inspection, OEM or a process control application, Micro Epsilon measurement engineers can provide the right measurement solution.

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