This digital measuring device optionally displays the voltage of the on-board battery and the starter battery. The stresses are displayed as exact numerical values. The additional bargraph display works in the range from 10.5 to 15 volts and thus represents the most interesting range of battery voltage, from deep discharge to maximum charging voltage, clearly and at a glance. When the device is installed, 12V or 24V operation is set once for this function. In 24V operation, the range then corresponds to 21.0 to 30.0 volts. A mixed operation of e.g. 24V consumer starter circuit and 12V supply circuit is also possible, as this setting is made separately for the starter and on-board battery. The connection is made via screw terminals on the rear of the device. Suitable for the VOTRONIC modular system.