Strictly, if the barrier field in Fowler–Nordheim 1928 theory is exactly proportional to the applied voltage, and if the emission area is independent of voltage, then the Fowler–Nordheim 1928 theory predicts that plots of the form (log(i / V) vs. 1/ V) should be exact straight lines. However, contemporary experimental techniques were not good enough to distinguish between the Fowler–Nordheim theoretical result and the Millikan–Lauritsen experimental result.