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A new approach to position detection in short-stroke cylinders

Direct, continuous and fast monitoring

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The technology sector is constantly evolving - and sometimes these innovations are small at first glance, but bring significant benefits in application. We would like to introduce you to the BDF - an innovative ultrasonic position sensor that is the first of its kind. This sensor represents a significant improvement in the field of position detection, especially for hydraulic cylinders with a short stroke.

How it works

  1. The sensor is installed in direct contact with the hydraulic oil and can withstand a maximum pressure of 350 bar.

  2. It then emits an ultrasonic signal into the fluid.

  3. This ultrasonic signal propagates in the fluid until it is reflected. There are two types of reflection: a) Partial reflection at the integrated reference target to compensate for the speed of sound, which varies depending on the type of medium, temperature and pressure. b) Reflection at the bottom of the piston (target).

  4. The exact piston position is then determined using the time-of-flight method, taking into account the compensated speed of sound.

The BDF sensor offers several advantages, such as continuous measurement with high positioning accuracy and easy integration into existing designs without a mechanical connection to the piston. Due to its compact size, it requires less space. Other advantages include quick setup via the Balluff IO-Link standard and a teach mode for zero point correction.

Section through a short-stroke cylinder with built-in sensorSection through a short-stroke cylinder with built-in sensor

Thanks to its intelligent self-compensation, the sensor works reliably without recalibration. Its multifunctional interface (IO-Link, analog current/voltage, SIO) makes it compatible with a wide range of applications.

The BDF sensor is supplied with a comprehensive manual that includes installation recommendations. It also provides additional information on early fault detection.

Frequently asked questions

Can the sensor be operated in air or only in liquid media?
The sensor is designed for use in liquid media, typically hydraulic oil. If it is not in direct contact with the liquid, it indicates this by a status switch-off (red LED).

Does the sensor work with all common hydraulic fluids?
The sensor can work in any fluid, regardless of its composition or other factors such as pressure and temperature. The sensor continuously adapts to the ambient conditions, making it a versatile solution.


  • Sensors
  • Smart sensors
  • IO-Link

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Bernd Schneider

Bernd Schneider

Engineer with many years of experience in plant engineering and automation technology

2 Contributions


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Balluff GmbH

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73765 Neuhausen a.d.F.