Sonic Water Level Meter (Well Watch 660) External Power - 6.5 to 12VDC at 80ma max. Do not exceed 16V. Real time clock (included with DL, extended memory package) Li lon 3V battery CR2032. Accuracy - 0.1 ft (3 cm) Range - 10 to 2000 ft (3 to 600 m) Meter Dimensions - 8.25 x 3.5 x 3.5 inches