Use of barometer Pre-adjustment of the barometer, generally the barometer is calibrated in the factory under 400m above sea level. Due to the change of altitude in your location and the indication error caused by vibration in transit, the barometer need to be adjusted by the following steps 1. First, check the local atmospheric pressure at the local meteorological station or network, airport, or public building calibrated barometer, or use an existing barometer as the reference standard. 2. Carefully adjust the slotted screw on the back of the barometer until the pointer indicates the actual barometric pressure in the area. Do not adjust the barometer movement too much. When the adjustment is complete, gently tap the glass surface of the barometer by hand until the pointer Accurately indicate the actual pressure value. 3. The adjustment screw cannot be over-adjusted. If the screw is tightened in one direction, the end of the adjustment range has been reached.