In rain chamber, rain sprayer was fabricated above windshield glass and water sprayer equipping with different size of nozzles. In case when averaging function is enabled, the sensor output showed slower response than the case with peak function. The test under actual raining condition may differ from simulated response using rain sprayer. Natural raining condition is random, which is out of control, thus it is hard to evaluate the output. In this case prolonged exposure to outside raining condition may help to estimate the respons