Planimeter

The concept for an integrating planimeter was first put forward by the Bavarian land surveyor Johann Martin Hermann in 1814. A planimeter is an analogue device dating back to the early 19th century which is used to measure the area of a 2D shape. A mechanical planimeter is an example of a simple differential analyser. A differential analyser is a mechanical analogue computer capable of solving differential equations using the mathematical process of integration, performed using wheel-and-disc mechanisms. Planimeters are commonly used to measure areas under irregular curves. An example of a planimeter can be seen on display at The National Museum of Computing.