| 摘要 |
The invention relates to a monitoring device for determining the degree of transparency of window panes for automatically triggering a window pane cleaning process, in particular in windscreens of vehicles, consisting of a measuring device for the degree of soiling and degree of damage to the window pane, which device has at least one light-dependent measuring signal generator, at least one light-dependent comparison signal generator, which signal generators operate when the light conditions change, one comparison circuit and one evaluation and control circuit, and of a triggering device for the cleaning device and/or one warning device, the comparison signal generator having a surface, preferably in the form of a window pane, with increased hardness, to which a cleaning device is assigned. This is a supplement to the patent application P 3515409.8. The object of the present invention is to prevent considerably this wearing of the comparison signal generator. The invention consists in the fact that the comparison signal generator is provided on its front side with a shutter or flap which opens periodically.
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