The Wohler 7006 DM2000 portable differential manometer has + or - 800.00 inches WC measuring range and 0.01 resolution, and is used to troubleshoot and balance HVAC systems, including measuring draft and differential pressure in gas line and manifold applications. The accuracy is the greater of + or - 3%, or + or - 0.02 inches WC. An IrDA provides data output to an IrDA-compatible device (sold separately). It is powered by two AA batteries (included) and includes a 5ft. hose. SpecificationsPressure typesDifferentialMedia compatibilityGas line and manifoldPressure range+ or - 800.00 inches WCAccuracyGreater of + or - 3%, or + or - 0.02 inches WCResolution0.01 inches WCEngineering unitsWCData outputIrDAPower requirementsTwo AA batteriesDimensions6.6 x 2.2 x 2.1 inches (H x W x D)H is height, the vertical distance from the lowest to highest point; W is width, the horizontal distance from left to right; D is depth, the horizontal distance from front to back.Manometers measure the pressure of a liquid or gas. They are used in laboratory, medical equipment, engineering, automotive, and heating, ventilation, and air-conditioning applications. Manometers measure any combination of gauge, absolute, or differential pressures. Gauge pressure is the amount of pressure in a system relative to the ambient pressure, absolute pressure is the amount of pressure in a system relative to an absolute vacuum, and differential pressure is the difference between two pressures. Analog manometers are composed of columns of liquid, and they use gravity and the liquid's density to calculate pressure. Because they have no moving parts, analog manometers do not require re-calibration. Digital manometers have pressure sensors that are connected to a system with a hose to provide a digital readout of the amount of pressure present in a system. They use microprocessors to calculate pressure, and they require periodic calibration to help ensure accuracy.What's in the Box?Wohler DM2000 differential manometer5 ft. hose(2) AA batteriesInstructions