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Construction
The FlexiForce A201 force sensor is an
ultra-thin, flexible printed circuit. The
force sensors
are constructed of two layers of substrate
(polyester/polyimide) film. On each layer, a
conductive material (silver) is applied,
followed by a layer of pressure-sensitive
ink. Adhesive is then used to laminate the
two layers of substrate together to form the
force sensor. The active sensing area is
defined by the silver circle on top of the
pressure-sensitive ink. Silver extends from
the sensing area to the connectors at the
other end of the sensor, forming the
conductive leads. A201 sensors are
terminated with male square pins, allowing
them to be easily incorporated into a
circuit. The two outer pins of the connector
are active and the
center pin is inactive.
How
it Works
The FlexiForce single element force sensor
acts as a force sensing resistor in an
electrical circuit. When the force sensor is
unloaded, its resistance is very high. When
a force is
applied to the sensor, this resistance
decreases. The resistance can be read by
connecting
a multimeter to the outer two pins, then
applying a force to the sensing area. In the
image below, the plot shows both the Force
vs. resistance and Force vs. conductance
(1/R).
Note that the conductance curve is linear,
and therefore useful in calibration.
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