DESIGN AND DEVELOPMENT OF MEDICAL ELECTRONIC ...

RESPONSIVE SIMULATORS 295One Teledeltos Square∂Jy[ Jy +∂yδy ] δxJxδyδyδx[ Jx +∂Jx∂xδx]δyJyδxTeledeltos Torso cut-outHigh InputImpedanceDVMDCSupplyV to I ConverterPin holed regionCarbon PaperGraph PaperFigure 6.32 Teledeltos paper is a resistive paper that has uniform resistance. It can be cut to the scaled shape of the body region to be investigated.Electrodes painted with conductive ink allow connection to current–voltage sources. Inhomogeneities are introduced by means ofperforations or silver spots (e.g., pinhole region simulating lungs). Field intensity values are read with sharp-tipped voltmeter probes. A sheetof carbon copy paper and graph paper make it easy to trace equipotential lines and gradients.Consider how Teledeltos can be used to solve electrical field problems. The current flowis essentially in two dimensions (i.e., across the surface of the paper but not through itsthickness from one face to the other). Suppose that the vector J(A/m) represents the currentdensity per unit width at some point on the Teledeltos sheet. Then the electric field (orvoltage gradient) at the same point in the sheet isE Jρ(V/m)where ρ is the specific resistance of the sheet. Teledeltos paper has a uniform grid printedon it, and ρ represents the resistance between opposite sides of a grid square.