Abstract: Measurement devices are provided on the boom and stick of an excavator and are diposed to measure, by means of the gravitational force, the angle of the boom and the stick, respectively, relative to the horizontal plane. These measurement values are applied to an evaluation instrument which indicates the excavation depth on the basis of the length of the boom and the stick and with the help of the received values. Furthermore, means may be provided to measure the lifting force exercised by the boom ram, this measurement being also applied to the evaluation instrument whereby it can, by means of the first-mentioned measurement values, also indicate the turning moment exercised on the boom and the stick.