How are Kestrel Meters wind speed readings so accurate?

For more than 15 years, Kestrel has used a wind tunnel to make sure their Kestrel Meters are fully calibrated to the highest standards before they leave our facility. However, they have recently switched from an open loop tunnel to a closed loop tunnel. Closed loop wind tunnels have a strong advantage over open loop designs mostly due to the precision and consistency that the closed loop offers, especially at lower wind speeds. The closed loop design also allows for less power loss and less turbulence while in use. Temperature in a closed loop tunnel can also be controlled more easily due to lesser influence from outside airflow entering into the chamber.