Delft University of Technology

Low-cost Capacitive Personnel Detector

R.N. Aguilar, , M. Roelofsz, H. Kerkvliet,

R. van de Ven, G.C.M. Meijer Electrical Instrumentation Laboratory, Microelectronic Department,

Delft University of Technology, The Netherlands

Delft University of Technology

Contents

• Introduction: Tracking systems

• Capacitive sensing• Electrode overview

• Two-port technique• Three-signal technique• Implementation• Conclusion

Delft University of Technology

Sensing technique ?

Tracking

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Sensing technique

Delft University of Technology

Capacitive sensing

A r e aC =

d i s t a n c er o

high dielectric constant !

H

D

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Electrode overview

Delft University of Technology

Two-port technique

*feet xm air

feet x

C CC C

C C

Delft University of Technology

*feet xm air

feet x

C CC C

C C

Two-port technique …

Delft University of TechnologyThree-Signal Technique

Delft University of Technology

X k C Cm m offset

m m

reference reference

X XX Cm offsetX X X C

reference offset

X k C Creference reference offset

X Coffset offset

Three-Signal Technique …

Delft University of Technology

Micro-controller

Electrodes

ControlLines

UniversalTransducerInterface (UTI)

Switches and Buffers

ControlLines

Display

Signal-Processing Circuit

Implementation

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Implementation …

STD=0.001pF

Res=10bit

Delft University of Technology

Thank You