The first anemometers were developed centuries ago, and have taken a variety of forms. Over time, scientists learned what configurations work best, and because of this knowledge, the most common designs nowadays tend to either incorporate spinning wind cups or propellers.
Wind Cups - Many weather sensors employ a three-cup configuration that spins on a horizontal plane as the wind passes through it. The horizontally-arranged three-cup design works extremely well because it can measure wind speed no matter what direction the wind is coming from. Testing has shown over the decades that three-cup designs generate a higher and more consistent amount of torque, and respond to wind gusts more quickly than other cup configurations. In addition, aerodynamically-optimized cups capture the maximum possible amount of wind force on the open side, propelling the cup forward, while the streamlined front of the cup slices through the air as it goes through its rotation. The wind cups also offer a dual bearing design to eliminate shaft flex and wobble, which can compromise accuracy.
As the wind cups spin, they turn a small drive shaft with a magnet positioned at the bottom end. The magnet passes over an electrical sensor called a reed switch. When exposed to a magnetic field, two tiny metal reeds are joined together, completing an electrical circuit. Each time the circuit is completed, an electrical impulse will be sent to a digital processor. Based on the frequency of the impulse, the processor can calculate a wind speed reading.
Propellers - The propeller design, such as used for portable handheld anemometers, operates on a vertical plane, requiring the user to manually face the anemometer in the direction the wind is coming from. As the propeller spins, it also causes a magnet (located at the center of the propeller) to rotate. Nearby, a small magnetic field sensor detects this rotation, passing on electrical impulses to the anemometer’s processor. The frequency of the impulses is translated to a wind speed reading.
Why Is It Beneficial to Have an Anemometer?
Benefits, depending on how you use your anemometer, can include safety, protection of personal property, home improvement, property management, and getting the most out of your favorite recreational activity such as finding the best wind conditions for boating or ideal wind conditions for golfing.