Level Switches

Level switches are used to detect liquid or powder levels, or interfaces between liquids. These level measurements are indicated via an electrical switching action. These are typically point level switches, measuring whether the level of a container has reached or gone over a predetermined point. However, switching mechanisms can be integral to continuous level switches as well. Multiple point switches can be integrated together to give a stepped version of continuous level. These level switches can be used either as an alarm device or as control switches, turning something on or off, such as a pump, or sending a signal to a valve actuator. What makes level switches special is that they have a switched output and can be either electromechanical or solid state, either normally open or normally closed.

The typical options for poles and throws are available. Most switches have either one or two poles and one or two throws, but some manufacturers will produce custom level switches for special applications.

The measuring range is probably the most important specification to examine when choosing level switches. Also of critical concern are the ratings for current and voltage the switches require.

Depending on the needs of the application, level switches can be mounted a few different ways. These switches can be mounted on the top, bottom or side of the container holding the substance to be measured. Among the technologies for measuring level are air bubbler technology, capacitive or RF admittance, differential pressure, electrical conductivity or resistivity, mechanical or magnetic floats, optical units, pressure membrane, radar or microwave, radio frequency, rotation paddle, ultrasonic or sonic and vibration or tuning fork technology. Analog outputs from level switches can be current or voltage signals. Also possible is a pulse or frequency. Computer signal outputs that are possible are usually serial or parallel.

Level switches can have displays that are analog, digital or video displays. Control for the devices can be analog with switches, dials and potentiometers; digital with menus, keypads and buttons; or controlled by a computer. Some features that can make level switches more desirable are being programmable, having controller, recorder or totalizer functions and a built-in alarm indicator, whether audible or visible. Also important for some applications are sanitary ratings and the ability to handle slurries with suspended solids, such as wastewater or sewage.

• Switch Tips: Ultrasonic level switches
  Ultrasonic switches transmit a signal in the range of a few megahertz to a receiver across a gap. The signal attenuates severely when passing through air, but the presence of liquid greatly enhances...
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• Deltapilot S Hydrostatic Pressure Sensors and Liquiphant Level Switches Monitor Storage Tank Levels
• Conductivity Level Switches
  Conductivity switches are solid-state devices that detect the presence or absence of electrically conductive liquids. They do so by sending a small current through their probe tip. Current flowing...
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Part Numbers for Level Switches