This German made barograph uses eight diaphragm bellows to provide maximum sensitivity and precision. The hinged case provides easy access to the chart drum. The single AA battery operated quartz movement requires no winding and is more accurate than key wound movements. The conventional ink bin and messy ink bottle are replaced by a felt tip pen which lasts 6 to 9 months. The barograph is furnished with a one-year supply of weekly charts AA battery one felt tip pen and dampening fluid. Case dims: 11 in x 6-3/4 in x 6-1/2 in. Chart size: 3-1/16 in x 12 in. Chart range: 28.5 to 31 inches. Chart duration: 7 days.