Float
Simple and suitable for liquids. Float position operates one or more contacts. Useful for tanks, basins, pumps and alarms.
Point level detection
Level switches
When only presence or absence needs to be detected, a level switch is often simpler and more robust than a continuous transmitter. Select the technology for fluid, density, viscosity, coating, pressure/temperature, connection and fail-safe function.
Displacer / cage switch
Uses changes in buoyancy. Suitable for pressurised vessels, boilers, separators and industrial applications with an external chamber.
Vibrating · VEGA
VEGA vibrating fork level switch for low or high level detection. A change in vibration indicates product presence; select materials and connections for the process.
Capacitive · VEGA
The VEGA level switch detects changes in capacitance between the probe and product. It works with liquids, pastes, powders and granules, but coating and dielectric variations must be considered.
When to use it / when to consider alternatives
Which level switch should I choose?
| Technology | Where it works well | Consider |
|---|---|---|
| Float | Clean liquids, simple control, several setpoints on one stem. | Density, viscosity, moving parts and mechanical clearance. |
| Displacer | Pressurised vessels, boilers, severe service and external chambers. | Density, cage mechanics, maintenance and equalisation. |
| Vibrating | Liquids, reliable high/low detection, moderate coating and no moving parts. | Minimum density, extreme viscosity and deposits bridging the fork. |
| Capacitive | Liquids, pastes, powders and granular products; compact geometries. | Variable dielectric properties, buildup, grounding and calibration. |
| Magnetic switch on KM26 | When a magnetic gauge is already installed and adjustable external alarms are needed. | Depends on reliable float movement in the chamber. |
Best practice
Installation and safety logic
For high-high or low-low protection, define the required response to power loss or a fault.
Filling jets can cause false switching, vibration or coating.
Consider immersion depth, sensor size and clearance from the bottom or nozzle.
Assess cleaning, special coatings or a technology less sensitive to deposits.
Safety thresholds must be testable; provide access and periodic testing.
Sensor position and delays must avoid cycling and provide effective pump protection.
ABB magnetic switches
LMS100 / LMS200 on KM26
LMS100
Magnetically operated SPDT switch outside the process. Adjustable setpoint on the chamber without new connections.
LMS200
DPDT switch in an industrial enclosure, designed for demanding conditions and alarm/ON-OFF functions on magnetic level gauges.
ABB documentation
ABB datasheets and manuals
Download the documents for your model. Shared manuals, protocols and versions are identified in each document card.
LMS100
External switch for magnetic indicators. Italian manual rev. A predates English rev. C.
LMS200
Request a quotation
Configure the level switch
Technical FAQ
Frequently asked questions
Vibrating fork or float?
A vibrating fork has no moving parts and tolerates many process conditions well; a float is simple and intuitive but depends on density and free mechanical movement.
Is a vibrating level switch affected by density?
Minimum density remains a selection parameter, but the principle is much less dependent on dielectric constant than capacitive measurement.
When should I choose capacitive detection?
When detecting liquids, pastes, powders or granules with a predictable change in capacitance. It is also useful where moving mechanical parts are undesirable.
What does fail-safe high / low mean?
It defines output behaviour under a fault or power loss, consistent with the high-level, low-level, overflow or dry-run protection function.
Can I use a level switch in a SIL application?
Only if the device and configuration are suitable for the required safety function. Being a level switch does not automatically imply SIL certification.
How do I protect a pump against dry running?
A low-level switch can provide a permissive or trip, but its location, response time and fail-safe logic must be designed for the plant.