A method and device for measuring voltage of an internal reference voltage source of an integrated semiconductor circuit, in particular, a DRAM, including the steps of comparing a reference voltage to an external comparison voltage with a comparator, forming a measured value for the reference voltage to be set in accordance with a comparison result, switching a commutator by a clock- or software-control to alternatively apply the reference voltage and the comparison voltage to the comparator inputs at the same time, varying one of the reference and comparison voltage to a setpoint voltage value until the comparator output changes its logic value at each commutator switched stage, buffering the voltage values present for each switched state when the logic value changes, forming an average value for the reference voltage from the stored voltage values, and setting the reference voltage as a function of the average value formed.