Circuit for checking an LED display

摘要

The invention relates to a circuit for checking an LED display for digital display units, in particular for scales which must be calibrated by statute. The aim of the invention is automatically to detect with a low outlay malfunctions in an LED display, such as interruption or short circuiting of display segments, as well as malfunctions in the associated drive circuits. The object is achieved by checking the voltage drop across each display segment. In this process, use is made of an operational amplifier with an open-collector output whose negative operating voltage is raised such that when an external reference voltage is used a low signal is generated at the output of the operational amplifier only when the display segment is illuminated. The invention can be applied in the case of digital LED displays in which the accuracy of the displayed value is of great importance and malfunctions have to be detected automatically. <IMAGE>