What's the principle of automatic induction wipers?
At present, two kinds of mainstream sensors are optical sensors and capacitive sensors, which work according to the refraction principle of light.
There is a light-emitting diode in an optical sensor that emits a conical beam of light that passes through the front windshield. When there's no Rain Water on the windshield and it's dry, almost all the light is reflected on an optical sensor, and when it rains, there's a Rain Water on the windshield, and some of the light goes off. This results in changes in the total amount of light received by the sensor, which detects the presence of Rain Water. The larger the area in which an optical sensor can receive reflected light, the more detailed information is obtained. Optical sensors are so accurate that it may even be possible to accurately determine the number of raindrops falling on the induced region. The other is a capacitive sensor designed primarily to take advantage of the huge differences in the dielectric constants of water and glass. The dielectric constant of water is 80 and the dielectric constant of glass is
2. Normally, two parallel finger metal plates are placed inside the windshield, and between the outer layers, one finger metal plate intersects but does not touch the other finger metal plates.
When the windshield is dry, a dielectric is formed between the outer surface of the windshield and each group of finger metal plates.
When the windshield becomes wet, the dielectric constant of the windshield varies according to the amount of water in contact with the windshield. If the sensor is mounted on the surface of the windshield or on the lower surface of the windshield, this is beneficial to the work of the sensor because it enables the sensor to perform its optimum sensitivity. The disadvantage is that installing the capacitive sensor on the outer surface of the windshield will cause the same problem as the resistance sensor, and the metal coating will be quickly blown off the windshield during the long term work of the wiper.
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