Testo 511 measures absolute pressure with an accuracy of +/-3 hPa. It is then converted to barometric air pressure by entering on-site height above sea level. Barometric elevation measurement between two points is also possible. Measures absolute pressure, e.g. for absolute pressure compensation in flow velocity measurements with a Pitot tube. Calculation of barometric air pressure. Barometric altitude measurement. Accuracy +/-1.2 in H20. Protective cap for safe storage. Including wrist strap and belt clip. Backlit display. 8 switchable pressure units: hPa, mbar, Pa, mmH2O, mmHg, inH2O, inHg, psi. 32 to 122 degree F operating temperature. 2 AAA battery type. 200 hours of battery life. Measures 4.5" length by1.7" width by 1" height. Probe type: Absolute pressure probe. Measuring range 120.4 to 481.8 H2O. Accuracy: +/- 0.01 H2O. Resolution: +/- 1.2 H2O.