Liquid level switches are useful in many contexts. In fuel storage tanks, for example, tank level indicators can be used to prevent the tank from becoming overfilled during a refilling process. These measurement technologies may include sensors using differential pressure sensing, optical sensing and control, sonic or radar, microwave and pressure-sensing membranes. These switches and their sensors can, if necessary, be finely tuned to measure extremely minute changes in liquid levels.
Liquid levels are measured by the activating or deactivating of a reed switch, relay or a solid-state switch. When the switch's circuit is completed or broken, the signal sent from the switch can be relayed to open or closed valves, operate pumps and initiate other processes. Simple optical sensors, for example, involve the use of LED systems. An LED is used to shine an infrared light through a tank. If the light beam is interrupted, a signal is sent to control equipment indicating levels.
Liquid level switches can be constructed from a variety of materials, including bronze, plastic, PVC, stainless steel and many other materials. They may also be constructed to withstand high temperatures and pressures, and PTFE switches are available for use in high-purity applications. Liquid level switches have a variety of applications including flow line monitoring, household appliances such as heaters and furnaces, automotive, and control technology.
There are many different liquid level switch configurations. The simplest liquid level switch variety is the float level switch, which involves a hollow buoy attached to indicating circuits. When the enclosure in which the level switch is installed is empty, the buoy hangs toward the bottom of the enclosure because of gravity. When the enclosure is sufficiently filled, the rising liquid line causes the buoy to rise. If the buoy rises enough, the circuit in the indicator will close. A signal is then sent from the indicator to gauges or control equipment. Most other liquid level switch varieties are a variation on that design.