A fork suits liquids and many powders and granules. A single rod, like the VLS, gives material no gap to bridge between tines, and suits powders, granules and other free-flowing solids.

Do I need to set it up for each liquid?

Usually not: the switch reacts to the damping of the fork, which liquids cause. Very light, aerated or foaming media are worth checking with us first.

How do I use it for dry-run protection?

Mount it where the pump draws its liquid — in the tank near the outlet, or in the suction pipe — and use its output to stop the pump when the fork is uncovered.

Can it work in a hazardous area?

Yes, with a certified version: the Delta Mobrey DMS & DMT, for example, come in ATEX-approved variants. We check the certification for your zone.

LEVEL MEASUREMENT TECHNOLOGIES

Vibrating level switches: tuning forks and rods for liquids and solids

A vibrating level switch tells you whether a liquid or a powder has reached a point — for overfill and dry-run protection, and for high and low alarms in tanks and silos. It has no moving parts that wear, and works in liquids, powders and granules. Our catalogue includes the Klay Vibraswitch-C and Vibraswitch-S tuning forks for liquids, the Delta Mobrey DMS & DMT forks for liquids and solids, and the Delta Mobrey VLS vibrating rod for bulk solids.

See the vibrating level switches

How a vibrating level switch works

A drive in the switch, usually piezoelectric, keeps a fork or a rod vibrating at its resonant frequency. In air it vibrates freely. When a liquid or a powder covers it, the medium damps the vibration and lowers its frequency; the electronics detect the change and switch the output.

The Delta Mobrey DMS & DMT, for example, keep the fork in resonance with an electronic circuit, detect the damping when material touches it, and switch the output relay after a configurable delay — so that splashes and falling powder do not cause false alarms.

The Klay Vibraswitch-C and -S are tuning forks for liquids, with viscosities up to 10,000 cSt, process temperatures from −40 °C up to +100 °C (C) or +120 °C (S), pressures up to 40 bar, and insertion lengths from 47 mm to 3 m. The Delta Mobrey VLS uses a vibrating rod for powders, granules and other free-flowing solids, with an LED that shows the switch state.

The vibration of the fork at its resonant frequency, in air
The electronics, which keep the fork in resonance and detect the change
The switch point: the level at the tines of the fork
The level, rising towards the switch point
The output, which changes state when the medium covers the fork

Where a vibrating level switch fits — and where it does not

A strong choice for

Overfill protection on storage and process tanks
Dry-run protection for pumps, in the tank or in the suction pipe
High and low level in silos of powders and granules
Liquids of very different kinds, including viscous ones — up to 10,000 cSt on the Vibraswitch
Hygienic tanks, with smooth wetted parts and hygienic connections, as on the Vibraswitch

Think twice when

You need the level itself, not a limit: use a level transmitter
The medium leaves heavy, hard build-up that bridges the tines
Large lumps or falling material could hit the fork: protect it with a baffle, or choose a rod
The switch would sit in the filling stream, where splashes cover it

How it compares with the other technologies

Typical process temperature of each technology, in °C. The technology of this article is highlighted.

Hydrostatic level transmitters−20…+100 °C
Radar level−40…+200 °C
Ultrasonic level−40…+80 °C
Vibrating level switches (the technology of this article)−40…+120 °C
Floats and displacers−60…+320 °C
Conductive and HF level switches−30…+150 °C
Rotating paddle−20…+80 °C

Typical process temperatures, not a model commitment; several technologies have versions for higher temperatures. We confirm the figures of each instrument for your application.

All technologies

Installing a vibrating level switch

Mount the switch at the level you want to detect: near the top for overfill, near the bottom or in the pump suction for dry-run. In liquids, a fork through the side wall is usually mounted horizontally, with its tines turned so that the liquid drains between them.

Then:

Overfill protectionThrough the side wall, above the highest normal level, so that the switch changes over before the tank overflows.

Dry-run protectionIn the suction pipe before the pump, so that the pump stops when the pipe runs empty.

In a siloA rod through the wall, sloping down, so that powder slides off it instead of piling up on top.

Keep the tines away from the inlet stream and the wall, and out of nozzles where product can stay between them.
In silos, protect a rod or a fork from falling material with a baffle above it.
Choose the switching mode for the function, so that the output goes to the safe state if the power fails.
Test the switch periodically by covering the fork, or with the test function where the electronics have one.

Vibrating level switches by industry

ChemicalOverfill protection on storage tanks of chemicals and solvents.

Food & BeverageTanks of milk, juices, syrups and oils, with hygienic connections.

Oil & GasOverfill and dry-run protection in hazardous areas, with ATEX-approved versions.

Mining, Minerals & MetalsHigh and low level in silos and bins of cement, lime and minerals, with vibrating rods for solids.

Water & WastewaterDry-run protection for pumps, and high-level alarms in tanks.

Vibrating level switches in our catalogue

The vibrating level switches in our catalogue, each with its own page and technical data.

All vibrating level switches

DELTA MOBREYVibrating Fork Level Switch - DMS & DMTCompact vibrating fork level switch for reliable point-level detection in solids and liquids. View product

DELTA MOBREYVLS Vibrating Rod Solids Level SwitchReliable single-point level detection for bulk solids with vibrating rod technology and external LED status indication. View product

KLAY INSTRUMENTSVibraswitch-CVibraswitch-C: reliable electronic tuning fork level detection for industrial liquids across wide temperature and pressure ranges. View product

KLAY INSTRUMENTSVibraswitch-SRobust tuning fork level switch with stainless steel construction for reliable detection across all liquid types and demanding process conditions. View product

Vibrating level switches: frequently asked questions

Ask about a vibrating level switch

Tell us the medium, the function (overfill, dry-run, high or low level), the process temperature and pressure, the connection and the output you need — and our engineers will suggest the right switch, with price and delivery time.