What is the principle of automobile air conditioning air volume measurement?

Hello, I don’t know if it is too late to give you an answer now, as shown in the picture; this equipment is a testing equipment for testing the air volume distribution of automobile air conditioners. This equipment is According to the air chamber method in the GB1236-2000 standard, the air volume is tested. The upper part of the equipment is a plexiglass wind tunnel, and the cabinet below is the electrical control and data acquisition system; it mainly collects the static pressure blown out by the air conditioner, and the nozzles on both sides of the wind tunnel are Differential pressure, temperature, humidity and atmospheric pressure inside the wind tunnel, the air volume is calculated based on these data, and the equipment can also test the blower inside the air conditioner. Condensation fan and evaporation fan, and test fan voltage, current, power and efficiency, etc. I don’t know if I can still understand.