The FSR 404 model is a single-zone Force Sensing Resistor® based on the FSR 402 but has been designed with a hole in the middle to allow for use in applications where it can be mounted over a boss, a bolt, or some other protrusion. While many of the 400 series sensors are optimized for use in human touch control of electronic devices this sensor is designed for applications including 3D printer bed leveling, installations with tight space constraints, and where a thin form factor—such as a washer-like configuration—is required. This is a two-wire device. FSR’s are robust polymer thick film (PTF) sensors that exhibit a decrease in resistance with inversely corresponding to the increase in force applied to the surface of the sensor. The FSR 404 sensor has an outer diameter of 20mm and a 5.5mm cutout in the middle. The active sensing area of the ring is only 4.35mm wide, but by having a force concentrating actuator ring built into the device, its force sensing capabilities are enhanced. The standard connection method is solder tabs, but other custom connector options can be made available upon request. Interlink Electronics FSR 404 is part of the single-zone Force Sensing Resistor family.