Highest precision mass spectroscopy and other highly accurate measurements have been carried out in Penning traps with metal electrodes painstakingly shaped along hyperbolic contours. A single electron has now been observed in a much simpler, cylindrical trap with equally good signal‐to‐noise ratio, thus demonstrating the possibility of conducting such experiments in a more readily constructed apparatus and opening the possibility of some new experiments. An essential requirement is the careful choice of electrode lengths to make the size of the electric quadrupole potential insensitive to adjustments which minimize deviations from an electric quadrupole.