I'm trying to deeply understand how the air-flow sensors mounted inside heaters works. They are composed of a U-shaped PCB with an NTC on each end. For example:
This PCB is inserted into a tube where the air must flow. If one of the NTC was shielded from the air-flow I can guess you can detect the movement due to the lowering of the temperature measured from the other sensor.
But because both will be affected by the air-flow it's not clear to how to measure such a movement.
Is this solution effective also in open air? I mean, placing this kind of sensor at the center of a room, could it detect any movement in any direction?