App note about conductive plastic used on motion transducers from Vishay. Link here (PDF)
The polymer film track has a conductive plastic paste laid upon it. This paste includes an inert filler of carbon black which constitutes the basis of Vishay SFERNICE’s technology for manufacturing precision potentiometers.
The resistive track obtained can be used:
• inside a cylindrical housing for making a rotational potentiometer
• on a flat support when manufacturing a linear motion transducer.
This method of producing the plastic film creates a resistive track which is exceptionally uniform in its resistivity and which allows excellent results regarding linearity.