Do you want to build a Magnetostrictive Position Sensor as described in: https://de.wikipedia.org/wiki/Magnetostriktiver_Wegaufnehmer

In short: A current pulse will initiate a torsion wave along a magnetostrictive wire at the position of a moving cursor magnet. The travelling torsion wave generates a signal in a receiver coil. From the time between current pulse and the signal pulse the position of the magnet (the distance between receiver coil and magnet) can be determined.

Note: Current development and discussion can be found here: https://hackaday.io/project/202298-magnetostrictive-position-sensor Here you can also read more about signal recording schemes and alternative counter electronics.

Here is a set of parts to build a Magnetostrictive Position Sensor. With this sensor you can measure the position of a magnet sliding along a PVC tube surrounding a magnetostrictive Nickel wire. You can use it to build a linear servo with a DC motor. The sensor is scalable as working range depends on the length.

UPDATE 10.2.2025: I have added a radial manget holder which can hold up to 6 4mm Nd cylinder magnets. This holder creates very clean and strong wavelet pulses.

UPDATE 5.3.2025: There is now an end piece with tensioner consisting of the parts: Halter, Klemme_Bottom, Klemme_Top and Mutter

The proposed 3D fittins are compatible with fischertechnik construction system. It consists of following parts:

1. Magnet Holder for Ring magnet
2. End clamps (you need 4 pieces)
3. Coil body
4. Connector block for coil
5. Wire guide (print it upright with 0.1mm resolution, supports from build plate and large brim)
6. Coil holder block for Fsichertechnik (part that can be used to mount coild to the Fischertechnik system if no tube is used)

To build this sensor followng additional parts and components are needed:

• Nickel or NiFe wire (for heating applications) , Diameter: 0.8mm, Length: 60cm (for a 50cm sensor, but longer wires should be possible)
• Nd Ring Magnet: Outer diameter: 12 mm, inner diameter, 8.5 mm, height: 4mm (I used: fix-o-moll Neodym Magnete Ringe 12mm silber )
• PVC housing tube, Outer diameter: 7mm, Inner diameter: 5mm, Length 50cm (You can chose your desired length; It might be possible to use Aluminium tubes)
• 12 x M3-Screws with sink head:, Length 10-15mm
• Power Supply for excitation puilse: 10-20V
• Separate Power Supply for analog electronics: 5-10V (Deriving Voltage from excitation power supply with an additional regulator should be possible)
• Cu-Wire: 0.1-0.3 mm, for 800 Windings
• Exciter-Circuit with a good Power-Mosfet (*)
• Analog Circuit (*)
• Gate Circuit
• Selector-Circuit
• Arduino Uno (*)
• Arduino Software

*: The princible and the sensor electronics is described in ft-pedia 2024/4: https://ftcommunity.de/ftpedia/2024/2024-4/ftpedia-2024-4.pdf

FreeCAD-File to adjust the fittings and an experimental Arduino-Sketch are included