CST – Computer Simulation Technology

Microdul Gains Deeper Insight into Finger Detection Sensors with CST EM STUDIO

The challenge: Reliability of electrostatic proximity sensors in a difficult environment

Microdul produces proximity sensor chips that can be used with remote sensing plates. Changes in plate capacitance are detected by a digital auto-calibrating algorithm. An approaching human finger typically causes a switching operation. This principle is demonstrated in Figure 2. The capacitive switch can be used for many non-contact applications. The main challenge is to develop a sensor which can reliably distinguish between intentional switching operation and environmental interference.

Figure 1: Finger sensor application.


Microdul investigated the influence of different grounding arrangements on the sensor’s capacitance. Figure 2 shows a finger model placed above two sensor plates. The objective is to obtain the influence of the ground rings....

 Figure 2: Finger model above sensor plates with ground rings (enclosing the sensor plates).

The plots of the electric potential distribution show how the field is constrained by the ground rings. This constriction is highlighted by arrows in Figure 3.

Figure 3: Double sensor plate: Electric potential distribution with ground rings.

By using the integrated parameter sweep of CST EM STUDIO (CST EMS) the capacitance can be rapidly and efficiently obtained for different values of the permittivity (εr) and the panel thickness (d_Panel) for configurations with and without ground rings. Figure 4 shows these results.

Figure 4: The sensor’s capacitance is slightly higher without ground rings.

CST Studio Suite helps to understand the sensor’s electrostatic behavior better

The main benefit gained by using CST Studio Suite is an improved understanding of the effect of design parameters on the performance of the sensing plate. CST EMS helps Microdul to support existing or potential customers more efficiently with their individual needs with proximity sensors. This deeper insight allows Microdul to provide their customers with higher-quality application notes.

The combination of accuracy and speed in CST EMS is the most significant advantage for Microdul. Reliable simulation results are available within a reasonable time. The software is intuitive and easy to use, since using an EM simulation tool was completely new to Microdul. All models were created in CST EMS using the powerful built-in 3D modeler with its parameterization capabilities. The “parameter sweep tool” turned out to be a very useful function since multiple simulations could be run over night to obtain results for the complete parameter space.


CST software has definitely improved our knowledge about EM fields. With the newly obtained knowledge we can now better advise potential customers. We believe that this puts us ahead of our competitors. The CST software definitely met our expectations. The intuitively usable software is working efficiently and is stable.


  • Roger Infanger
  • , Microdul AG
  • Grubenstrasse 9, CH - 8045 Zürich, Tel: +41 44 455 35 27, Fax: +41 44 455 35 95

Rate this Article

5 of 5 Stars
5 Stars
4 Stars
3 Stars
2 Stars
1 Stars
Microdul AG is a specialist in high quality microelectronics. Microdul has a broad range and depth of experience. Thanks to Microdul‘s three business lines, Module, Thick-film, and Semiconductors, there is a wide spectrum of choice with respect to electronic miniaturisation. Microdul’s core competence is the production of cutting edge individual solutions in close cooperation with the customer.
contact support

Your session has expired. Redirecting you to the login page...

We use cookie to operate this website, improve its usability, personalize your experience, and track visits. By continuing to use this site, you are consenting to use of cookies. You have the possibility to manage the parameters and choose whether to accept certain cookies while on the site. For more information, please read our updated privacy policy

Cookie Management

When you browse our website, cookies are enabled by default and data may be read or stored locally on your device. You can set your preferences below:

Functional cookies

These cookies enable additional functionality like saving preferences, allowing social interactions and analyzing usage for site optimization.

Advertising cookies

These cookies enable us and third parties to serve ads that are relevant to your interests.