Constructing a capacitive sensor using springs 2

The electric field propagating from the solid-state conductive sensor to the finger is emitted from the upper surface of the sensor. Figure 2 shows that the electric field propagating from the spring (cylinder) to the finger is emitted from the upper and side surfaces of the sensor. That is to say, the sensitivity of the spring is slightly better than that of solid-state conductive sensors with thicker cover layers, because the spring sensor can form a larger electric field. The above assumption has been confirmed by calculating the touch capacitance value, and we will discuss this issue in detail in the next section.  diode

Simulation of finger touch sensing capacitor

In order to clarify the effect of the thickness of the cover layer on the increase in capacitance (FTC) of finger touch, we still used the same solid-state conductive sensor and spring sensing simulator for modeling, but increased the thickness of the cover layer from 1 millimeter to 10 millimeters.  diode

In addition, in order to determine the optimal physical size of the spring, the correlation of FTC will be modeled based on parameters such as its height, diameter, and spring wire thickness. Figures 4 to 6 show the relationship between FTC correlation and different simulation parameters.

Analysis of simulation results

It can be clearly seen from Figures 1 and 2 that when the finger is placed on the sensor, the sensitivity of the spring and solid-state conductive sensor is the same. When the finger position is slightly offset from the center of the sensor, the sensitivity of both sensors will decrease, but the sensitivity of the spring sensor is slightly stronger than that of the conductive sensor. When the finger placement position deviates, the strong signal on the spring sensor is a major advantage of the spring sensor, especially in slider applications (as shown below), and this advantage is even more pronounced.  diode