SENSITRONICS Force Sensing Resistor

Force Sensing Resistor

See also: FSR 101...

The FORCE-SENSING-RESISTOR (FSR) is made of a proprietary polymer thick film ink, typically screen printed on Mylar (PET) film, depending on the requirements of the application. As force is applied to the device, the electrical resistance decreases. The ink formulation can be customized for application-specific requirements, such as minimizing saturation with greater force, as well as for very low forces needs. Temperature, humidity, and shear are some of the considerations.

The Force-Sensing Resistor can be used for such applications as computer input devices, musical instruments, interactive toys, robotics fingertips, automotive, sports, or medical applications.

Sensitronics offers the two basic FSR configurations; the ShuntMode and the ThruMode. Both are constructed of two substrates, or film layers. The proprietary force-sensing resistor ink (FSR element) is screen printed on one film, while on the other film is printed the conductive, interdigitated electrode fingers. The two films are assembled with the printed surfaces facing each other and can be adhered together with a double-stick adhesive spacer around the perimeter. The interdigitating conductive fingers can also be made on a printed circuit board. When a force is applied to the device, the shunt or shorting circuit is complete. The more force applied, the more conductive the output. The sensor can be read by connecting an ohmmeter to the two contact legs of the sensor and applying a force to the sensing area.

The ThruMode device is also printed on two film layers. Conductive pads, which can be made of silver or silver/carbon blend ink, are first screen printed on each of the substrates. The force-sensing resistor ink is then screen printed over the conductive pads. These two printed substrates are then assembled facing each other. Adhesive can be used to laminate the two substrate layers together and as a spacer. The more force applied to the ThruMode device, the more conductive the output.