Unfortunately, there is no example of Bar Proximity Sensor (a) length in Figure 3-37. CapSense-Based Proximity Sensing with PCB Trace.
(AN64846 Getting Started with CapSense : https://www.cypress.com/file/41076/download)
Also, there is no Graph showing the relationship between the proximity-sensor bar size and the proximity-sensing distance, such as Figure 3-38.
AN64846 Section 3.6.3 Factors Affecting Proximity Distance mentions
“It is very difficult to derive a relationship between the sensor size and the proximity-sensing distance. Depending on the end-system environment, the proximity-sensing distance may vary for a specific sensor size. You can find the sensor size needed to achieve a required proximity-sensing distance by making sensor prototypes. You can use a copper foil, as Figure 3-39 shows, to make a quick sensor prototype to determine the sensor size needed to achieve the required proximity-sensing distance.”
So, It would be better to understand what the requirement and evaluate/determine the sensor size needed to achieve the required proximity-sensing distance by prototype testing.
Thank you for your support