Recommendations for pucks to use with Flexiforce sensors
Question/Problem: What do you recommend for pucks?
Answer/Solution: Using a puck to ensure proper loading of the sensing area is a good idea, but the material depends on your application.
To use fingertips during abdominal palpation, you probably want to use a thin (1mm or less) disk comprised of a soft urethane (to allow the disk to contour around the fingers so a doctor can properly administer a palpation with minimal interference).
For applications where 2 plates are coming together or in cases of pure compression a more rigid puck comprised of metal or hard urethane works well to concentrate the forces onto the sensing area.
Whenever using a puck, make sure to use it in the calibration as well since interface materials play a major role in how the sensor responds to forces.
Finally, make sure the puck is slightly smaller than the sensing area (in this case the sensing area of the A-201 FlexiForce sensor is 0.375” diameter, so a good rule of thumb is about 80% of that or a puck of ~0.3” diameter should suffice). The reason the puck should be smaller than the sensing area is because the top conductor and bottom conductor are not always perfectly concentric so a puck that fits either conductor perfectly will most likely encompass some non-active area. Also, having a puck that is smaller than the sensing area allows for some small movement of the puck over time or from one actuation to the next without having to worry that it has moved out of the sensing area.
