Measuring Airflow In An HVAC System

[Nubmian] wrote in to share his experiments with measuring airflow in an HVAC system. His first video deals with using with ultrasonic sensors. He found an interesting white paper that described measuring airflow with a single-path acoustic transit time flow meter. The question was, could he get the same effects with off-the-shelf components?

[Nubmian] created a rig using a pair of typical ultrasonic distance sensors. He detached the two transducers from the front of the PCB. The transducers were then extended on wires, with the “send” capsules together pointing at the “receive” capsules. [Nubmian] set the transducers up in a PVC pipe and blew air into it with a fan.

In his second video, [Nubmian] sets up a test rig consisting of a multimeter connected to an airflow sensor. The multimeter is soon replaced by an Arduino with the help of an AD623ARZ amp. The wires for that setup needed some shielding. Aluminum foil connected to the ground did the trick.

For more HVAC projects check out this pinwheel flow meter and [Adam]’s piece on HVAC techs, hackers who make house calls.

10 thoughts on “Measuring Airflow In An HVAC System

  1. I wanted to measure the airflow from my office outlet vent. An old PC fan worked great connected to an ESP to read the speed counter they have built-in. Maybe not as advanced and can’t read low flows, but it worked well in that application. Placed it on top of the vent inside the feed duct.

    1. I built a very simple airflow meter with a 5V pc fan (3 wires) coupled with a waterflow meter purchased on aliexpress. ok, the readings are in l/min but gives me a good indication of the air flow to know when to change my filter.

  2. Very cool. I wish I could find a way to plot the leaking Freon in a system. Its so much fun and inspiring to see you guys doing this. I look forward to watching more and learning and maybe one day contributing.

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