Johannes Meier (18) wants to make life easier for forestry workers. To this end, he developed a measuring device for chainsaws that enables the operator to quickly and precisely cut felled trees into pieces of a specified length without the need for any other tools. All the operator has to do is move the rolling saw chain along the trunk. The distance covered is shown on a display integrated into the saw's air filter cover. This principle of measuring is known from the bicycle speedometer: Seven small magnets are attached to the circumference of the chain drive sprocket at regular intervals. The rolling chain turns the wheel and the magnets are moved past a sensor. A microcontroller then calculates the distance traveled from the magnetic pulses.