Experimental Validation of Capacitive Touch Sensors: Recommendations for Human Machine Interface Design

Capacitive touch sensors use the electrical properties of capacitance to detect contact with anything conductive. The client, a home appliance manufacturer, utilizes capacitive touch sensors, called keys, in many of their products. In this case, the human body acts as the conductive object, providing input for the capacitive touch sensing. This project aims to validate the simulation of keys through experimental results and then provide a recommendation for a Human Machine Interface (HMI) design guideline for specific keys. Data was collected via proprietary software provided by the client. A testing procedure was designed with various specifications including the following: approach speed, distance between the surface of the key and the probe, contact location on the key, probe diameter, and contact duration. The new procedure necessitated building a testing rig to ensure consistent measurements while reducing errors in the data. The proposed testing procedure was validated with a Measurement System Evaluation (MSE). The compiled data included the change in capacitance (delta) and the status (ON or OFF) of the key. From this, a heat map outlining the area of each key that can successfully register capacitive touch was produced. Synthesizing this information validated the simulation results. The intent of the authors was to make a recommendation on the continued use of the simulation and the need for validation. While the ultimate goal was to develop practical design guidelines for HMI applications, beyond this immediate project, the hope was to contribute to more robust and user-friendly HMI systems across a wide range of capacitive touch applications in consumer and smart electronics.