Multichannel electric field sensors are used for electrical impedance and capacitance tomography applications. In cases where only one-sided access can be accommodated, fringing electric field sensors (FEF) sensors are used. The genera! design principles of multichannel fringing electric field sensors are discussed in This work. Analysis of the figures of merit of FEF sensors, such as penetration depth, signal strength, measurement sensitivity, and imaging resolution, are presented. The effects of design parameters on sensor performance are also evaluated. The qualitative design principles described in this part of the paper provide intuitive guidelines for the simulation-based design optimization procedure to be presented in the second part of the paper.