Abstract: A device for measuring the voltage of a voltage source includes a number of temperature responsive displays and a circuit including a number of heating circuits, each heating circuit for heating one of the temperature responsive displays when a threshold voltage of the heating circuit is exceeded, and a printed resistor, each heating circuit being connected to a length of the printed resistor such that the voltage of the voltage source at which each heating circuit heats a temperature responsive display is a function of the ratio of the lengths of the printed resistor to which the heating circuits are connected.