Ultrasonic Karman Vortex Air Flow Meter
Install the ultrasonic transmitting probe and the receiving probe opposite to each other on both sides of the downstream pipeline of the Karman vortex generator. Due to the influence of the Karman eddy current on the air density, the time of the ultrasonic wave from the transmitting probe to the receiving probe will be later than that without the vortex, resulting in a phase difference. By processing this phase signal, the vortex pulse signal can be obtained,
How Hot Wire Air Flow Meters Work
When there is no air flow, the bridge is in a balanced state, and the control circuit outputs a certain heating current to the heating wire resistance RH; when there is air flow, the heat of RH is absorbed by the air and becomes cold, its resistance value changes, and the bridge loses Balance, if the temperature difference between the hot wire resistance and the intake air is kept constant and a certain value, the current IH flowing through the hot wire resistance must be increased. Therefore, the hot wire current IH is a function of the air mass flow.