B2.2 - Electrode Design for Capacitive Sensors
- SENSOR+TEST Conferences 2011
2011-06-07 - 2011-06-09
- Proceedings SENSOR 2011
- B2 - Sensor Design and Modeling
- H. Zangl - Graz University of Technology (Austria)
- 234 - 239
This paper presents a fast method for the design of electrode topologies of capacitive sensors with the aim to provide a good signal to noise ratio.
Frequently, the initial electrode design for capacitive sensors is chosen according to the knowledge of an expert and optimization is done in time consuming experiments. An alternative approach is given by model based optimization using field computation software and standard optimization techniques. However, this is still a complex task as the locations and dimensions of electrodes span a huge parameter space.
Theoretically, a capacitive sensor could use an infinite number of tiny electrodes, impress voltage on these electrodes and measure the displacement currents. The determination of all inter-electrode capacitances would be impossible, as the number of combinations is infinite. However, only certain voltage patterns will provide a high sensitivity with respect to the parameters of interest. In this sense, it is reasonable to search for voltage patterns that maximize the local relative sensitivity at a certain surface point. Using the Finite Element Method, the voltage distributions with maximum uniform sensitivity (all local relative sensitivities are equal) can be found by solving an eigenvalue problem. Electrode topologies are obtained by approximating the distribution(s) with a small number of discrete electrodes. It is demonstrated that the impact of the discretization on the relative sensitivity can remain low and thus that the method can be used to find appropriate electrode topologies.