There are three different types of charts – strip, circular, and roll. The chart recorder takes data and then uses some type of marking mechanism to record it on a piece of paper. In strip charts used today, the recorder uses a pen and ink reservoir. Some of the chart recorders use thermally sensitive paper and a heated pen to make the marks, and others use electrical signals on electro-sensitive paper. The charts typically use a galvanometer to drive the marker. However, there are also a number of modern recorders that are making use of embedded computers systems that feature a microcontroller, a printing device, and an analog to digital converter.