The FPA is designed to determine the Zeta Potential of fibers according to the Helmholtz-Smoluchowski equation by simultaneously measuring conductivity, pressure and the streaming current potential. The measuring principle is based on the streaming current potential measuring method in a fiber plug. That fiber plug is automatical build up on a screen electrode in the measuring cell of the FPA by (with the help) a vacuum. By periodically changing the vacuum during the measurement the charge clouds absorbed on the fibers are moving with the liquid stream and generating the streaming current potential measured by the screen and ring electrode.
The knowledge of the fiber charge enables a correct and effective dosage of the charged chemical additives. The fiber adsorption of cationic starch, wet strength resin, and many other chemical aids can be easily measured with original samples on-site to optimize the dosage of chemicals in the wet end of the paper manufacturing process.