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1/27 Precision PositioningCapacitive Distance Sensors for Wijnand Harmsen, PME – Mechatronic System DesignJune 28 th, 2010 The Excessive Humidity Effect.

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Presentation on theme: "1/27 Precision PositioningCapacitive Distance Sensors for Wijnand Harmsen, PME – Mechatronic System DesignJune 28 th, 2010 The Excessive Humidity Effect."— Presentation transcript:

1 1/27 Precision PositioningCapacitive Distance Sensors for Wijnand Harmsen, PME – Mechatronic System DesignJune 28 th, 2010 The Excessive Humidity Effect on Challenge the future Delft University of Technology

2 2/27 Precision Positioning Position sensor Contactless Resolution Accuracy Sensor volume Introduction

3 3/27 22mm Capacitive Distance Sensor Introduction Electrode spacing d 50 µm transmitting electrode sensing electrode readout Resolution: <1 nm, Accuracy: <10 nm

4 4/27 The Excessive Humidity Effect Introduction transmitting electrode sensing electrode readout Resolution: <1 nm, Accuracy: <10 nm nm

5 5/27 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 6/27 Outline Water layers Measurement setup Humidity response Conclusions & recommendations Water layers / Setup / Humidity response / Conclusions

7 7/27 Water layers Adsorption Water layers / Setup / Humidity response / Conclusions sensing electrode 0.6 nm 0.3 nm

8 8/27 Water layers Adsorption sensing electrode Water layers / Setup / Humidity response / Conclusions transmitting electrode

9 9/27 Indirect Weight 6 nm Polarization1 nm Attraction force 100 nm Capacitive (el. field) nm Water layers Measurement Water layers / Setup / Humidity response / Conclusions Schwartz, 1994Motschmann & Teppner, 2001 Worldpress.com Wang & Kido, 2003 Max. water layer thickness

10 10/27 25°C 50% RH 35°C 50% RH Measurement Setup Requirements Water layers / Setup / Humidity response / Conclusions Offset / gain error Relative / absolute humidity Thickness of nm  Multiple distances  Different temperatures  1 nm resolution  1 nm stability Double measurement setup Transmitting electrode Sensing el. Requirement

11 11/27 Measurement Setup Capacitive measurement Water layers / Setup / Humidity response / Conclusions Transmitting electrode Sensing el. Insulator Conductor  Multiple distances  Different temperatures  1 nm resolution  1 nm stability 50 µm

12 12/27 Measurement Setup Capacitive measurement Water layers / Setup / Humidity response / Conclusions  Multiple distances  Different temperatures  1 nm resolution  1 nm stability Insulator Conductor

13 13/27 d Laser Camera Measurement Setup Reference measurement Water layers / Setup / Humidity response / Conclusions  Multiple distances  Different temperatures  1 nm resolution  1 nm stability

14 14/27 Measurement Setup Double measurement setup Water layers / Setup / Humidity response / Conclusions Laser Camera  Multiple distances  Different temperatures  1 nm resolution  1 nm stability

15 15/27 OpticalCapacitive Measurement Setup Double measurement setup Water layers / Setup / Humidity response / Conclusions  Multiple distances  Different temperatures  1 nm resolution  1 nm stability

16 16/27 Measurement Setup Double measurement setup Water layers / Setup / Humidity response / Conclusions Laser Camera  Multiple distances  Different temperatures  1 nm resolution  1 nm stability

17 17/27 Humidity response Input Water layers / Setup / Humidity response / Conclusions

18 18/27 Humidity response Measurements Water layers / Setup / Humidity response / Conclusions

19 19/27 Humidity response Measurements Water layers / Setup / Humidity response / Conclusions

20 20/27 Water Measurement distance Temperature Optical measurement Time response Humidity response Water layer presence Water layers / Setup / Humidity response / Conclusions Water Optical measurement Time response

21 21/27 Humidity response Optical measurement Water layers / Setup / Humidity response / Conclusions Water Optical measurement Time response

22 22/27 Humidity response Optical measurement Water layers / Setup / Humidity response / Conclusions Water Optical measurement Time response

23 23/27 Humidity response Time response Water layers / Setup / Humidity response / Conclusions Water Optical measurement Time response

24 24/27 Humidity response Time response Water layers / Setup / Humidity response / Conclusions Water Optical measurement Time response

25 25/27 Humidity - Capacitive sensor readout Humidity - Water adsorption Conclusions Water layers / Setup / Humidity response / Conclusions Capacitive precision measurements will be even more precise

26 26/27 Different materials Water layer influence on optical measurement Nonlinear time dependency Conclusions Recommendations Water layers / Setup / Humidity response / Conclusions

27 27/27 Questions

28 28/27

29 29/27 Marek & Straub, 2001

30 30/27 Water layers / Setup / Humidity response / Conclusions

31 31/27

32 32/27 Water layers Disturbance

33 33/27 Measurement Setup Reference measurement Water layers / Setup / Humidity response / Conclusions

34 34/27 Water layers / Setup / Humidity response / Conclusions Material type Surface roughness Contamination

35 35/27 Water layers / Setup / Humidity response / Conclusions

36 36/27 Wang & Kido 2003 Water layers / Setup / Humidity response / Conclusions

37 37/27

38 38/27

39 39/27

40 40/27

41 41/27 Water layers / Setup / Humidity response / Conclusions

42 42/27 Humidity response Water layers / Setup / Humidity response / Conclusions Electrod e spacing [μm] Temperat ure [°C] Initial humidity level [%] Final humidit y level [%] Difference between both sensors Δ d [nm] Settling time [h]

43 43/27 Drinks: Next Friday 21:00 “De Ruif”


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