Electrostatic sensors have been successfully used in the field of particle flow measurement due to the advantages of simple structure, robustness and low cost. Recently, advances have been made in developing electrostatic sensing techniques for rotational speed measurement. The geometric shape and size of the electrodes have significant effects on the performance of electrostatic sensors in terms of spatial sensitivity and temporal frequency response. This paper focuses on the theoretical analysis and experimental assessment of strip and butterfly shaped electrodes for rotational speed measurement of a metallic shaft. Spatial sensitivity and filtering effect of the sensors are investigated through mathematical and computational modelling. Analytical and experimental results suggest that the butterfly shaped sensor outperforms the strip sensor in terms of spatial sensitivity, power spectral density and signal bandwidth.