【Monitoring Mode & Sound and Light Alarm】When the micron vacuum gauge is turned on, it defaults to normal mode, short press the "SET" button to enter the monitoring mode. If the current pressure is lower than the set pressure, the backlight of the HVAC vacuum gauge will flash and the buzzer will sound continuously. When the pressure is greater than the set pressure, the alarm will disappear automatically (press any key or the alarm can be automatically disarmed after 30 seconds). 【Large Display Supports Backlight & ℃/℉ Switching】The 4.2CM×4.8CM high-definition display screen supports LCD backlight, which can display clear data even in dark or weak light conditions. When the digital micron vacuum gauge is turned on, short press the "ON/OFF" button to turn on and off the backlight. “UNITS” button: short press to switch pressure units, long press to switch temperature units. 【High Precision Sensor & 13 Pressure Units】The micron vacuum gauge uses a professional micron-level sensor for more accurate measurement. Measuring range: 0-100KPa/14.50Psi/750061umHg (micron), resolution: 0.001Kpa/1umHg, accuracy: ±0.1%FS. The HVAC micron vacuum gauge supports 13 units: mmHg, inHg, umHg, ftH2O, cmH2O, inH2O, Pa, Kpa, mbar, bar, Kg/cm², psi, oz/in². 【High Measurement Accuracy】The digital manometer air and gas pressure tester adopts a high-quality pressure sensor, which has the characteristics of high precision and wide range. High-precision ADC and low-power MCU. Maximum/minimum mode and DIF mode. Range: ±2.999psi; Accuracy: ± 0.3% FSO (at 25℃); Repeatability: ± 0.2% (Max ± 0.5% FSO); Linearity/Hysteresis: ± 0.29%FSO (25℃). 【Positive and Negative Pressure Measurement】There are two ports on the top of the manometer, one for testing positive pressure and the other for testing negative pressure. You can select any port to test the pressure difference (P1-P2) between the two areas. Using the single pipe connector of the air pressure meter, you can quickly measure the current pressure value (relative to the current atmospheric pressure).