Abstract: Apparatus for measuring a resistor in function of the amplitude of a direct current or the frequency and the amplitude of an alternating current. When the direct current equipment of this apparatus is used, the direct current signal flowing through the resistor is generated from an adjustable direct current generator and produces between terminals of the resistor a direct voltage signal which is chopped and amplified into a recurrent rectangular signal having a predetermined frequency and an amplitude proportional to the resistance value of resistor and included within a predetermined measurement interval. When the alternating current equipment of this apparatus is used, a first alternating current signal flowing through the resistor is generated from an adjustable frequency generator, an adjustable amplitude attenuator and a voltage-to-current converter.