  Low frequency AC-measurements are commonly used to determine the voltage and
currents through mesoscopic devices. We calculate the effect of the alternating
Hall voltage on the recorded time-averaged voltage in the presence of a
top-gate covering a large part of the device. The gate is kept on a constant
voltage, while the Hall voltage is recorded using an integrating
alternating-current lock-in technique. The resulting Hall curves show
inflection points at the arithmetic mean between two integer plateaus, which
are not necessarily related to the distribution of the density of states within
a Landau level.
