Binary sensors are contact devices. A switch is placed on the inner surface of each finger of a manipulator hand. This type of sensing is useful for determining if a part is present between fingers. By moving the hand over an object and sequentially making contact with its surface. Multiple binary touch sensors often mounted on the external surfaces of a manipulator hand to provide control signals useful for guiding the hand throughout the workspace.

Analog sensors

An analog touch sensor is a compliant device whose output is proportional to a local force. This device consists of a spring loaded rod which is mechanically linked to a rotating shaft in such a way that the displacement of the rod due to a lateral force results in a proportional rotation of the shaft. The rotation is then measured continuously using a potentiometer or digitally using a code wheel. Knowledge of the spring constant yields the force corresponding to a given displacement.

During the past few years, considerable effort has been devoted to the development of tactile sensing arrays capable of yielding touch information over a wider area than that afforded by a single sensor. The use of this devices in which the inner surface of each finger has been covered with a tactile sensing array.

Sensing arrays can be formed by using multiple individual sensors, one of the most promising approaches of this problem consist of utilizing an array of electrodes in electrical contact with a compliant conductive material whose resistance varies as a function of compression. This devices are often called artificial skins, an object pressing against the surface causes local deformations which are measured as continuous resistance variations.