Cold plasma-based dual cathode anemometer for simultaneous air speed and flow angle sensing

Cold plasma-based dual cathode anemometer was used to achieve the simultaneous sensing of air speed and flow angle. Cold plasma (corona discharge) was incepted with high voltage of 2500–2800 V using a pin anode and dual plane cathodes. Ion clouds were formed between the anode and cathodes and were displaced upon interaction with air flow. The ion displacement manifest as changes in cathode currents and thus output voltages across the series resistors. Using air speeds of 0.09–2.72 m/s directed at flow angles of −30° to 30°, the output voltage responses showed adequate uniqueness to distinguish between different air speeds and flow angles. Since the responses are coupled, the output voltage sum and ratio between the two cathodes were calculated and used as metrics. The output voltage sum predominantly represented the air speed while the output voltage ratio primarily indicated the flow angle. These two metrics could be used as inputs into an iterative scheme to determine the air speed and flow angle. The proposed anemometer also had stable zero flow response and was robust to sudden air flow stop because it did not have moving parts. Given its tiny sensing volume of 3.2 × 3.2 × 3.0 mm³ and low power consumption (<25 mW), its applications can span conventional scenarios as metrology as well as recent advancements in carbon emission management and smart cities analytics.