Force Sensing Resistor

A Force Sensing Resistor ( FSR) is a registered U.S. trademark name of a measuring element of the company Interlink Electronics, which changes its electrical resistance under the action of force or pressure.

The history of the FSR began in the 1980s. At that time, Mick Fleetwood was the drummer of the band Fleetwood Mac in search of a sensor for its electronic drums. Together with the later founder of Interlink Electronics, Inc., Michael Thoben, the FSR sensor has been developed. The company Interlink Electronics manufactures FSRs until today.

A FSR consists of a sandwich of two plastic films. One is on the inside of the FSR ink ( a graphite-containing semi-conductive paste) coated and the other with two comb-shaped interdigitated conductive contact bars. However, they are electrically insulated from each other and have external connections. The two films are joined together by means of a double-sided adhesive layer. It also ensures that the coated " active" regions of the films is practically not touching in the unloaded state. Only under the action of pressure or force on the sandwich the contact grid of the FSR ink are electrically connected to each other and one can measure the electrical resistance of the structure to the external terminals. At rest, this resistance is several megohms ( milliohms ). With increasing force, the resistance decreases because the active areas of the FSR sensor always get more intimate contact. This is up to the saturation limit which is about 1 k and a pressure of 100 N / cm ².

The FSR from the beginning was so accurate that it could be used for many other purposes. Today you can find FSR sensors in the automotive sector, in peripherals of computers in medical applications and in touchpad for capturing electronic signatures.