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Rain-Sensing Wipers

Rain-Sensing Wipers

By Jeff Youngs, February 24, 2012
Windshield wipers, which have been standard equipment on most vehicles since 1916, were developed to improve visibility during inclement weather. For nearly 100 years, drivers operated the wipers with manual controls mounted on the dashboard. Today, technology has made possible motorized windshield wipers that automatically recognize a developing visibility problem and clear the glass before the driver can react to the problem.

The term "rain-sensing wipers" is commonly used for a system designed to clear the windshield of rain, snow, and debris without driver intervention. The system is programmed to automatically activate and alter the speed and rate of the wiper blades to keep outward visibility unobstructed at all times. A rain-sensing wiper system does not clean the windshield any better than a manual system; it simply monitors outward visibility and automatically activates the wipers.

How do they work?
The technology behind rain-sensing wipers is not complicated. A small area of the front windshield glass (usually located on the outside of the vehicle, opposite the rear-view mirror) is monitored by an optical sensor. The sensor is designed to project harmless infrared light at the windshield at an angle and then read the amount of light that is reflected back. A clean windshield will reflect nearly all of the light back, while a wet or dirty windshield will cause the light to scatter. The optical sensor can determine the necessary frequency and speed of the windshield wipers by monitoring the amount of light reflected back into the sensor.

As a safety precaution, and to prevent damage to the wiper mechanism, nearly all rain-sensing wipers must be activated each time they are used. The activation process prevents the system from automatically wiping a frozen windshield, or triggering while the vehicle is in a car wash; both instances could damage the blades or electric motor powering the wipers.

What are the benefits of rain-sensing wipers?
The benefits of a rain-sensing wiper system are most obvious during inconsistent rain or snow, when a standard wiper system requires constant attention by the driver to keep the windshield clear. Under such conditions, the rain-sensing system adapts to periods of heavy rain or snow and increases the speed of the wipers. During dry periods, when the windshield is clear, the wipers completely stop. If other vehicles splash or spray water or debris on the windshield, the rain-sensing system automatically intervenes by starting the wipers to keep visibility unobstructed.

How do they increase driver safety?
Many collisions are caused by driver distractions. Rain-sensing wiper technology allows the driver to activate the windshield wipers once, and then forget about them. The windshield wipers must be re-activated, however, if the vehicle has been turned off and re-started.

Do I need them?
Rain-sensing wipers are offered as standard equipment or as an inexpensive factory option on many new cars, light trucks and SUVs. There are also many systems offered by aftermarket suppliers. The wipers are easy to install; with just a single optical component, the technology can easily be adapted to any vehicle with electric wipers. Because they increase driving safety while reducing driver distraction and workload, rain-sensing wipers are a worthwhile improvement to any vehicle.
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