The Fixed-arm Polar Planimetershown in g. 2 representsthesimplestform ofan AMS_ER Planimeter. Itcan be madetoonescale only,and measurestheactual areaof ... The Sliding-arm (or Proportional) Polar Planimeter, ofwhich g. 4 represents the simplest form, has an adjustable tracing arm, divided into a number of scales, i.e.,