Differential pressure measurement in testo 510 is temperature-compensated for accurate readings. They can be displayed in Pascal over the whole measurement range. Magnets on the back of the instrument allow you to work hands-free. When used with a Pitot tube, testo 510 measures air speed. Air density can be compensated to give accurate readings. Display in Pascal optional over entire measurement range. Accuracy: +/- 0.01"H20 (0 to 0.12"H20)/+/- 0.02"H20 (0.13 to 0.4"H20). Temperature compensation. Magnetic back permits free-hand work. Flow velocity measurement with Pitot tube (Pitot tube not included in delivery). Air density compensation. Protective cap for safe storage. Including wrist strap and belt clip. Backlit display. Switchable units: hPa, mbar, Pa mmH2O, mmHg, inH2O, inHg, psi, m/s, fpm. Resolution 0.01 hPa. Operating temperature 0 to 50 degree C. 2 AAA batteries. 50 hours of battery life (average, without display illumination). Measures 119mm length by 46mm width by 25mm height (incl. protective cap).