Fig. 3: Directionality of the FCF sensor.

a Schematic of the experimental setup for directionality characterisation of the FCF sensor. b Regional enlarged view of FCF sensor, where the three thermistor pairs along the 0° airflow angle are P1–3 and those along the 90° airflow angle are V1–3. c Variation of output voltage V_out with airflow angle θ at 0.2 m·s⁻¹. d Simulated mean temperature difference ΔT_mean curves at the positions of the V1–3 thermistor pairs at 0.2 m·s⁻¹. The colour maps correspond to the local temperature distribution on the surface of the FCF sensor at airflow angles of 90° and 130°. e Variation of output voltage with airflow angle θ at 10 m·s⁻¹. f Simulated ΔT_mean curves at the positions of the V1–3 thermistor pairs at 10 m·s⁻¹, where 50°–130° and 230°–310° are the highly sensitive response intervals of V2 and V3.