These barometers can be found in the section to measure absolute pressure, differential pressure in respect to the atmosphere and negative pressure. There are barometers such as the DB2 digital barometers that have an internal memory for up to 750 readings and an analogue output of 0 to 1 volts. These barometers are perfect to measure atmospheric pressure, also called barometric pressure, is an expression for the weight of air (atmosphere) due to the earth's gravitational pull. This pressure at sea level is 1013.25 mbars (milibars). Thermo-Hygro barometers are also known as climate meters. With these barometers, you can ascertain not only barometric pressure, but also temperature and humidity. AVM-4000 series barometers are multi-function devices for measuring pressure, temperature, humidity and wind speed. Before being used, the barometers and Thermo-Hygro barometers have to be adjusted to 1013 mbars which is equivalent to the air pressure at sea level.