The working principle is that when there is horizontal wind in the environment, the special structure of the wind cup produces a directional rotation, driving the built-in sensor to generate voltage proportional to the rotation speed. The change in this signal voltage is displayed by connecting to a compatible pointer instrument. This sensor is self-powered and does not require external power. When wind causes rotation, a voltage signal is generated and displayed by the meter. This wind speed sensor has a simple structure and general accuracy. It is suitable only for environmental wind speed reference and not intended for weather forecasting applications. Color: black Material: ABS Package Contents: 1 x wind speed sensor with cable Note: Light reflection and different displays may cause the color of the item in the picture to vary slightly from the actual product. Measurement error allowance is +/- 1-3 cm. Only the items listed are included; other products are not included.