The working principle is that when there is horizontal wind in the environment, the special structure of the wind cup will produce a certain direction of rotation, driving the built-in sensor to generate voltage, which is proportional to the rotation speed. The change of this signal voltage is displayed by connecting to a specially customized pointer inst ent. This sensor is spontaneous and does not require power. When there is wind rotation, a voltage signal is generated and displayed by the meter. This wind speed sensor has a simple structure and general accuracy. It is only suitable for environmental wind speed reference and not for weather forecast applications.<br><br>The printing batches are different, the actual words may be different, but it will not affect the use Color: black Material: ABS<br><br>Package Contents: 1 x wind speed sensor with cable<br><br>Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.