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The point level switch is a simple device used in countless products from home coffee makers to industrial chemical tanks. These switches provide a simple on/off response when liquid level is at or past a certain point and can be set up to provide more sophisticated readings. The Simple One Level Switch Setup A single switch can let operators know when liquid levels fall outside expected parameters. A switch at the top of a tank can sound an alarm in case a stuck valve threatens to overfill the tank. One at the bottom can alert operators to unexpectedly low liquid levels that might indicate a leak. Level switches may be used to provide readings supplementary to other sensors. Consider the low-fuel light in automobiles. Even though there is a fuel gauge on the dashboard, most cars use level indicators to turn on a warning light when fuel is very low. The extra warning reinforces the message already given by the low reading on the fuel gauge, urging drivers to pull into a gas station and fill up. Use Two Switches to Define Boundaries In some containers, designers are interested only in showing whether liquid level is too high or too low. In many cases it is important to warn of both conditions. This may be a matter of convenience or it may be a safety issue. A common example is the automatically refilling tank. Two level switches are placed in the tank, one at the top and one at the bottom. Through normal use the liquid level in the tank drops. When it falls far enough it triggers the lower switch that activates a pump to refill the tank from a reservoir. The pump continues to move liquid into the tank until the level rises high enough to trigger the upper switch. This switch sends a signal to the pump to cease operation. Many Switches for Finer Control Several level switches can be installed in a tank to provide a simulation of a continuous level. If multiple switches are placed at equally spaced heights in the tank and hooked to corresponding lights on a panel, operators can tell at a glance roughly how full the tank is. Another use is to provide multiple levels of warning. For example, say there is a chemical plant with a tank that periodically needs to be refilled by ordering liquid shipments that come in by truck. One switch could be installed to light up a low level indicator on an operator panel so the refill can be ordered. A second switch lower in the tank could sound an audible alarm, allowing operators to decide whether to expedite shipment or shut down the process. A third switch near the bottom of the tank could automatically shut down the plant before damage is caused to the equipment.
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Author is a freelance copywriter. For more information on level switch, visit www.compac.com/.
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