Placom KP90N N-Series Roller-Type Digital Planimeter, Approximately 20 hours continuous operation, 8 Digit LCD Display, 6-digit pulse count operation that permits cumulative measurement of areas up to 10m-100 times the measuring capacity of ordinary planimeters, Include hold and measuring control, clear liquid crystal digital readout, and scale readings in either Metric or English, Comes packaged in a plastic carrying case with AC adapter (battery included) and operating instructions, Auto-Power-Off function