About Point Level Detection

Point level detection devices from Emerson™ are ideal for high and low alarms, overfill prevention, pump control and to detect the level at a specific point in your tank.


Prevent Overfills and Get Process Insight with Point Level Detection

Point level devices provide a simple, low maintenance technology for indicating the presence of liquids or solids. They are often installed as a high-level alarm for overfill prevention, and low-level alarm for tank or pipe empty detection.

It is good practice to fit high- and low-level alarm switches to tanks in addition to another measurement device.

Emerson™ has a wide range of point level devices including vibrating fork detectors, float and displacer switches, and ultrasonic level detectors.

How it Works

Rosemount 2100 Series uses vibrating fork technology. Designed around the tuning fork principle, it consists of a two-pronged fork which vibrates at its natural frequency. The frequency changes depending on the media in which it is immersed. When in air, the forks vibrate at their natural frequency. When liquid covers the forks, the frequency drops.

Changes to the frequency are continuously monitored by the switch electronics, which then change the output state to operate an alarm, pump, or valve.


Electromechanical float switches are mounted on the side or top of a tank, or in an external chamber, and rely upon the liquid buoyancy principle to lift the float until it reaches its single pre-set switching level.

The float carries a permanent magnet as part of the float assembly, which interacts with a second permanent magnet in the switch housing. The assembly is glandless as the magnets interact through the wall of the switch body to actuate or re-set a switching mechanism.


Displacer-type level switches rely on tension spring and liquid buoyancy principles to lift one or more displacer elements until they reach the single or multiple pre-set switching levels. They are used when one or more switching points are required a long distance below the mounting point.

Displacer elements are positioned on a cable suspended from a tension spring below the mounting point.


Ultrasonic point level detectors, or gap sensors, are typically used in non-hazardous area industrial processes to detect high or low liquid levels or liquid interface. The level detection is activated when there is a liquid present between the sensor’s transmitter and receiver crystals. In this way, the absence of liquid results in a low level indication. 

For interface detection between immiscible liquids, two techniques are available: ultrasonic attenuation and ultrasonic refraction.


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