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Level sensors are used to detect liquid or powder levels, or interfaces between liquids. These level measurements can be either continuous or point values represented with various output options. Continuous level sensors are devices that measure level within a specified range and give output of a continuous reading of level. Point level sensors devices mark a specific level, generally used as high alarm or switch.Multiple point sensors can be integrated together to give a stepped version of continuous level. These level sensors can be either plain sensors with some sort of electrical output or else can be more sophisticated instruments that have displays and sometimes computer output options. The measuring range is probably the most important specification to examine when choosing a level sensor. Field adjustability is a nice feature to have for tuning the instrument after installation.
Depending on the needs of the application, level sensing devices can be mounted a few different ways. These sensors 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 level sensors can be current or voltage signals. Also possible is a pulse or frequency. Another option is to have an alarm output or a change in state of switches. Computer signal outputs that are possible are usually serial or parallel. Level sensors 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.