DIELECTRIC: The ratio of the permittivity of a substance to the permittivity of free space. It is an expression of the extent to which a material concentrates electric flux and is the electrical equivalent of relative magnetic permeability. Relative to level control, the dielectric coefficient indicates the extent to which radar signal will reflect and relates to the strength of an RF capacitive measurement.

DISPLACER CONTROLLERS: As liquid level in a vessel increases or decreases, the buoyancy force on a displacer increases or decreases. The motion created by the change in force acting on a range spring causes movement of an attraction ball within an enclosed pressure-boundary tube.

DISPLACER SWITCHES: Operation is based upon simple buoyancy, whereby a spring is loaded with weighted displacers. Immersion of the displacers in the liquid results in a buoyancy force change, changing the net force acting on the spring. The spring compresses as buoyancy force increases. A magnetic sleeve is connected to the spring. Spring movement causes the magnetic sleeve to move into the field of a pivoted magnet, actuating a switch mechanism.

EXTERNAL CAGED SWITCHES: A style of float level switch where the float is housed in an external piping column (cage) attached to a vessel.

FLOAT LEVEL SWITCHES: All float-operated liquid level controls operate on the basic buoyancy principle. As the float rises or falls with liquid level, it moves a magnetic sleeve into or out of the field of a switch-actuating magnet, causing switch operation.

FLOW SWITCHES: Flow through a horizontal pipeline causes a pivoted vane assembly to swing in the direction of flow. The vane assembly lifts an attraction sleeve, which in turn causes a magnet to pull in and actuate the switch.

GUIDED WAVE RADAR: A type of radar level device that incorporates a probe called a waveguide and has superior performance in applications where turbulence, coating, build-up, and disturbances are present.

MAGNETOSTRICTIVE: A low energy pulse generated by on-board electronics travels the length of a magnetostrictive wire. A return signal is generated from the precise location where the magnetic field of a float intersects with the wire. To measure level, a timer precisely measures the elapsed time between the generation of the pulse and the return of the acoustic signal.

MLI: (Magnetic Level Indicators) Within a piping column is a float containing a group of magnets. A rise or fall of fluid in the process tank corresponds to a change within the piping column, and the float moves up or down accordingly. Clamped to the piping is a visual indicator housing with magnetic flags or a follower. Float movement rotates the flags and changes their visible color or moves the follower to the point of level.

PULSE BURST RADAR: Electromagnetic pulses are emitted into a vessel and reflect off of a liquid level surface where it is reflected as an echo back to an antenna. Electronics detect when the return echo is received and converts the time interval into a distance.

RF LEVEL CONTROLS: Utilizes the fundamentals of an electronic capacitor. A capacitor is formed when an AC signal is applied across two conductive plates separated by an insulating medium, or dielectric. The capacitance value increases as the dielectric increases, the plate size increases, or the distance between the plates decreases.

THERMAL DISPERSION: Operates on the basis of heat transfer and consists of a sensor with two RTDs. Gas or liquid flow across the sensor transfers heat from the reference RTD, creating a temperature difference between the RTDs, which is measured as flow.

Makes use of a pair of piezoelectric crystals at the tip of a transducer. When liquid is present in a gap between the crystals, the receive crystal senses ultrasonic signal from the transmit crystal and converts it back to an electrical signal. When there is no liquid present, the ultrasonic signal is attenuated and is not detected.

ULTRASONIC NONCONTACT: Transmitter that emits an ultrasonic pulse. The sound pulse is directed toward a liquid surface where it is reflected as an echo back to the transducer. Electronics detect when the return echo is received, and converts the time interval into a distance.

VIBRATION SWITCHES: Operates on the principle of detecting the dampening effect when solids are brought into contact with the vibrating rod.

The terms and definitions for this word search were provided by Jim Homoly of Magnetrol International, a manufacturer of flow and level measurement instruments.