Abstract: An amp-hour meter for a load driven by direct current, such as an electric vehicle, comprises a modulator connected across a resistor in series with the load for amplitude-modulating a pulse train from a multivibrator translated by a demodulator into a unipolar voltage varying with the load current. A sampler converts this voltage into a train of output pulses, generated at a rate proportional to the voltage level, whose count is numerically displayed as a measure of current consumption. The multivibrator, the demodulator, an intervening amplifier, the sampler and the display unit are serially energized with stabilized voltage and reduced current via a supply network connected across the load, this network including a ballast lamp in series with a Zener diode.