Anyone know where I can find Wire encoders that have an accuracy of 0.1 mm a length of approximately 200-300 mm ?
The only one I can find that comes close to this accuracy is A Celesco with an accuracy of 0.25 mm and a length of 500-600 mm.
Also anyone know where I can find good but cheap enough IMU = angle and acceleration sensors in one box (complete, not only chips). These would have to be small and easily mounted on a small cable (3 mm) and have to talk to a Siemens PLC through RS232 or 422 or Profinet,.. or wireless ones ?
I don't know about wire encoders (if you find a good part do let us know though).
eBay is worth checking for IMUs - there may well be cheap Arduino-compatible IMU
boards (there are many cheap sensor boards), things like the ArduPilot or similar which
combine a surface mount ATmega and accelerometer/gyro/compass sensors on a small
board sound like the sort of thing. There will be quite a range of such devices these
days I suspect. Or you could combine an Arduino Mini Pro and a sensor board (such
as the newer MPU-6050 breakout boards) to make a compact IMU package.
A wire encoder is going to be limited by the elasticity of wire, and I think that is a fundamental limitation. If you can buy a professional one with a particular accuracy, it's unlikely that you can get one with five times better accuracy.
Where do you get a requirement for 0.01 mm accuracy ? Perhaps you should be approaching your problem from another way.