Resistive Sensor Linearity Improvement Based on Change-Ratio-Decreasing and Change-Ratio-Increasing Subunits

To increase the linearity of the resistive sensor, a combined system composed of the change-ratio-decreasing subunit (CRDSU) and the change-ratio-increasing subunit (CRISU) is designed. In the CRDSU/CRISU, the change ratio of the output decreases/increases with the increase of the input. CRDSU and CRISU are used as the neighboring arms of the electrical bridge to convert the measured quantity to the output voltage. The combined system for the displacement sensor based on the piezoresistive effect of conductive polymer composite is developed as an example. The piezoresistive curve of the composite has a transition deformation. If the composite deformation is more/less than the transition deformation, the change ratio of the resistance decreases/increases with the increase of the displacement. To construct the combined system in which the varying tendencies for the change ratios of the resistances for CRDSU and CRISU are opposite, the initial deformations are applied on the subunits which are placed on the opposite sides of the measured workpiece. The experimental results verify the feasibility of using the combined system to improve the linearity.