The Dwyer HM28D3C10000 Handheld Digital Manometer 0-28 in. w.c., Error Limit 0.2% F.S. is a digital pressure measuring instrument with integrated pressure sensor for the measurement of differential or relative pressures. Features include: measurement in all common pressure ranges, display resolution to 0.001, differential or relative measurement, two line liquid crystal display, and adjustable auto power off to conserve battery. The HM28D3C10000 records up to 964 readings and offers up to 0.2% accuracy.