Liquid level floats are spherical or cylindrical objects that are buoyant in water and other liquids. They are used for surface demarcation and level measurement. They may also be incorporated into switch assemblies to control liquid level. Liquid level floats offer two choices for level measurement: continuous and multi-point. Continuous-level devices are designed to measure liquid levels within a given range. The output provides a continuous reading of the level. Point-level or multi-point liquid level floats mark a specific level and are used generally as a high alarm or switch. Some products integrate multiple-point liquid level sensors to provide a low alarm, or to serve as a stepped version of a continuous level. Liquid level floats may be categorized as gauges, sensor-only devices, sensor systems, and transmitters. These products carry specifications for measuring range and process operating conditions. The number of switch points, measuring range, and field adjustability are important measurement-range parameters to consider when selecting liquid level floats. Process operating specifications include maximum operating pressure, liquid specific gravity, material temperature range, and material density. The specific gravity of a liquid is a standard measure of its density, or mass per unit volume.
Liquid level floats differ in terms of output, mounting, and communication interface options. Analog voltage signals, analog current signals, frequencies or modulated frequencies, and alarms or visual indicators are the most common output options for these level sensing devices. Mounting options cover top, bottom, and side-mounted products. Some liquid level floats have a serial interface or use a serial communication protocol such as universal serial bus (USB), RS232, or RS485. Others have a parallel interface or use a parallel communications protocol such as general-purpose interface bus (GPIB).
Switch specifications for liquid level floats may be divided into configuration, pole and throw, and electrical switch categories. There are two choices for switch configuration: normally open (NO) and normally closed (NC). Pole and throw specifications are listed as single pole, single throw (SPST); single pole, double throw (SPDT); double pole, single throw (DPST); and double pole, double throw (DPDT). Maximum current, maximum AC voltage, maximum DC voltage, and compatibility with transistor-transistor logic (TTL) are key electrical-switch specifications to consider.
In terms of features, some liquid level floats are rate for sanitary applications or are suitable for use with slurries. Others are programmable, submersible, or equipped with a built-in alarm or indicator. Liquid level floats with controller and recorder or totalizer functions are also available.