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A force-sensing resistor is a material whose resistance changes when a force or pressure is applied. They are also known as "force-sensitive resistor" and are sometimes referred to by the initialism "FSR". Note that "FSR" is a trademark of Interlink Electronics, Inc.
The technology of force-sensing resistors was invented and patented in 1977 by Franklin Eventoff. In 1985 Mr. Eventoff founded Interlink Electronics, a company based on his patented invention, the force-sensing-resistor (FSR). In 1987, Eventoff was the recipient of the prestigious international IR 100 award for the development of the FSR. In 2001 Eventoff founded a new company, Sensitronics, which has become the leader in developing force-sensing resistor technology worldwide.
Force-sensing resistors consist of a conductive polymer, which changes resistance in a predictable manner following application of force to its surface. They are normally supplied as a polymer sheet or ink that can be applied by screen printing. The sensing film consists of both electrically conducting and non-conducting particles suspended in matrix. The particles are sub-micrometre sizes, and are formulated to reduce the temperature dependence, improve mechanical properties and increase surface durability. Applying a force to the surface of the sensing film causes particles to touch the conducting electrodes, changing the resistance of the film. As with all resistive based sensors, force-sensing resistors require a relatively simple interface and can operate satisfactorily in moderately hostile environments. Compared to other force sensors, the advantages of FSRs are their size (thickness typically less than 0.5 mm), low cost and good shock resistance. A disadvantage is their low precision: measurement results may differ 10% and more.
Force-sensing resistors are commonly used to create pressure-sensing "buttons" and have applications in many fields, including musical instruments, car occupancy sensors, Foot pronation systems and portable electronics.