✅【High Accuracy】Test air pressure ±13.79 kPa / ±2.000Psi with ±0.3%FS high accuracy. ±0.25%FS repeatability. 11 gas measurement units optional, including mmHg, inHg, ftH₂O, cmH₂O, KPa, Mbar, Bar, Psi, Kgcm², inH₂O, and Ozin². Over-range indication available. ✅【Dual Port Design】Equipped with two tube connector(3.18mm diameter), digital manometer 189A is capable to measure static pressure(positive/negative) and differential gas pressure levels accurately. An essential tool to obtain accurate pressure readings and diagnose issues in HVAC heating, ventilation, and air conditioning systems. ✅【Data Record & Zero-out】Press"REC" button to record and review max / min / average air pressure data; Short-press "HOLD” button to freeze measurement data and Long-press 5 seconds to clear out remaining dat.