The ALTA wireless air velocity sensor measures the pressure difference between two input ports, the temperature, and altitude determines the speed at which the air is moving in a system and transmits the measurement to iMonnit. The sensor measures the pressure difference between two ports. When viewing the sensor from the top, the right inlet port is the negative or low side pressure input. When the pressure on this port is greater than the left port the sensor produces a negative pressure reading. When the pressure is greater on the left port the sensor produces a positive pressure reading. Combined with the temperature and the altitude, the sensor determines at what rate the air is flowing in a system.