Precision Positioning

1. The Excessive Humidity Effect on Capacitive Distance Sensors for Precision Positioning June 28th ,2010 Wijnand Harmsen, PME – Mechatronic System Design Delft University of Technology Challenge the future

2. Precision Positioning • Position sensor • Contactless • Resolution • Accuracy • Sensor volume Introduction

3. transmitting electrode 22mm Electrode spacing d50 µm Capacitive Distance Sensor sensing electrode readout Resolution: <1 nm, Accuracy: <10 nm Introduction

4. transmitting electrode 200-800 nm The Excessive Humidity Effect sensing electrode readout Resolution: <1 nm, Accuracy: <10 nm Introduction

5. To find a relation between the change in humidity and the readout of the capacitive sensor and to find how this relation depends on the adsorption of water on the capacitive electrodes. Research Goal ? Introduction

6. Outline • Water layers • Measurement setup • Humidity response • Conclusions & recommendations Water layers / Setup / Humidity response / Conclusions

7. Water layers Adsorption 0.6 nm www.nasa.gov 0.3 nm sensing electrode Water layers / Setup / Humidity response / Conclusions

8. Water layers Adsorption transmitting electrode sensing electrode Water layers / Setup / Humidity response / Conclusions

9. Water layers Measurement Max. water layer thickness • Indirect • Weight 6 nm • Polarization 1 nm • Attraction force 100 nm • Capacitive (el. field) 200-800 nm Worldpress.com Wang & Kido, 2003 Schwartz, 1994 Motschmann & Teppner, 2001 Water layers / Setup / Humidity response / Conclusions

10. Measurement Setup Requirements Requirement • Offset / gain error • Relative / absolute humidity • Thickness of 1-800 nm • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Double measurement setup Sensing el. 25°C 50% RH 35°C 50% RH Transmitting electrode Water layers / Setup / Humidity response / Conclusions

11. Measurement Setup Capacitive measurement • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Transmitting electrode 50 µm Sensing el. Insulator Conductor Water layers / Setup / Humidity response / Conclusions

12. Measurement Setup Capacitive measurement • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Insulator Conductor Water layers / Setup / Humidity response / Conclusions

13. Measurement Setup Reference measurement • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Camera Laser d Water layers / Setup / Humidity response / Conclusions

14. Measurement Setup Double measurement setup • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Camera Laser Water layers / Setup / Humidity response / Conclusions

15. Measurement Setup Double measurement setup • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Water layers / Setup / Humidity response / Conclusions

16. Measurement Setup Double measurement setup • Multiple distances • Different temperatures • 1 nm resolution • 1 nm stability Camera Laser Water layers / Setup / Humidity response / Conclusions

17. Humidity response Input Water layers / Setup/ Humidity response / Conclusions

18. Humidity response Measurements Water layers / Setup/ Humidity response / Conclusions

19. Humidity response Measurements Water layers / Setup/ Humidity response / Conclusions

20. Humidity response Water layer presence • Water • Measurement distance • Temperature • Optical measurement • Time response • Water • Optical measurement • Time response Water layers / Setup/ Humidity response / Conclusions

21. Humidity response Optical measurement • Water • Optical measurement • Time response Water layers / Setup/ Humidity response / Conclusions

22. Humidity response Optical measurement • Water • Optical measurement • Time response Water layers / Setup/ Humidity response / Conclusions

23. Humidity response Time response • Water • Optical measurement • Time response Water layers / Setup/ Humidity response / Conclusions

24. Humidity response Time response • Water • Optical measurement • Time response Water layers / Setup/ Humidity response / Conclusions

25. Conclusions • Humidity - Capacitive sensor readout • Humidity - Water adsorption • Capacitive precision measurements will be even more precise Water layers / Setup/ Humidity response / Conclusions

26. Conclusions Recommendations • Different materials • Water layer influence on optical measurement • Nonlinear time dependency Water layers / Setup/ Humidity response / Conclusions

27. Questions

29. Marek & Straub, 2001

30. Water layers / Setup/ Humidity response / Conclusions

32. Water layers Disturbance

33. Measurement Setup Reference measurement Water layers / Setup / Humidity response / Conclusions

34. Material type • Surface roughness • Contamination Water layers / Setup/ Humidity response / Conclusions

35. Water layers / Setup/ Humidity response / Conclusions

36. Wang & Kido 2003 Water layers / Setup/ Humidity response / Conclusions

41. Water layers / Setup/ Humidity response / Conclusions

42. Humidity response Water layers / Setup/ Humidity response / Conclusions

43. Drinks: Next Friday 21:00 “De Ruif”