Trumen Vibrating Fork Level Switch for Liquids: LFV11 vs LFV12
A compact, no-moving-parts way to stop tanks overflowing and pumps running dry.
The Trumen vibrating fork level switch is a tuning fork that hums at its own resonant frequency. When liquid covers the tines, the frequency drops and the switch changes state — no float to stick, no calibration for each liquid. Trumen builds two compact versions, the short LFV12 and the longer LFV11, and we keep both in stock in Noida.
LFV12 and LFV11 Side by Side
| Feature | LFV12 (short fork) | LFV11 (long fork) |
|---|---|---|
| Fork length | 50 mm (excluding thread) | 128 mm (including thread) |
| Media | Liquids | Liquids and light solids |
| Process connection | ½", ¾", 1" NPT/BSP, Tri-Clamp 1"–1½", flush mount | 1" NPT/BSP, Tri-Clamp 1½"–2" |
| Max. pressure | 15 bar | 15 bar |
| Viscosity | Up to 10,000 cSt | Up to 10,000 cSt |
| Switching response | About 1 s | About 1 s |
| Outputs | PNP/NPN 12–60 VDC (250 mA), 8/16 mA loop, AC relay, NAMUR | Same electronics options |
| Housing | SS316/316L, IP65, power and alarm LEDs | SS316/316L, IP65, power and alarm LEDs |
| Best for | Pipes, small tanks, pump dry-run | Deeper nozzles, lagged tanks, granules |
Data from the Trumen LFV11/LFV12 datasheet and instruction manual. Confirm voltage and output against the order code on your unit.
How the Fork Knows It Is Wet
Piezo drive
A piezo-electric crystal keeps the two tines vibrating at their natural resonance in air — typically a few hundred hertz.
Frequency shift
Liquid around the tines adds mass, so the frequency falls. The electronics compare it with the dry value, not with the liquid’s conductivity or colour.
Switch and LEDs
Past the threshold the output changes state. A green LED shows power and a red LED shows the alarm, so you can test it by dipping the fork in water.
Because it reacts to density rather than electrical properties, the same LFV works in water, oil, solvents and milk without adjustment.
Where LFV Switches Earn Their Keep
Dairy and edible oil
High and low alarms on milk silos, CIP tanks and oil storage. Tri-Clamp versions suit hygienic pipework.
Fuel and lubricant tanks
Overfill protection on diesel day tanks, hydraulic reservoirs and lube-oil skids — foam and bubbles do not fool a fork.
Pump dry-run and flow
Mount an LFV12 in the suction line to stop a pump before it runs dry, or use it as a simple flow / no-flow indicator.
Trumen LFV Switches in Stock
Installing an LFV Correctly
- Never bend or machine the tines. Their spacing sets the resonant frequency; a bent fork will not switch reliably.
- Keep the cable entry pointing down. This stops condensation and rain running into the housing.
- Turn the tines to vertical on a side-mounted fork. The flat faces should stand upright so liquid drains off instead of sitting between them.
- Keep the fork out of the inlet stream. Liquid pouring directly onto the tines can trigger false alarms — move it or add a baffle.
- Leave room to pull it out. Allow at least 45 mm clear space beyond the fork for removal and cleaning.
- Pick the fail-safe mode. Choose maximum fail-safe for overfill alarms and minimum fail-safe for dry-run protection, so a cable break always gives the safe signal.
Trumen LFV Level Switch FAQs
What is the difference between LFV11 and LFV12?
LFV12 has a short 50 mm fork for pipes and small nozzles and is meant for liquids. LFV11 has a 128 mm fork (with thread) that reaches past thick walls or insulation and can also detect light solids.
Does foam or buildup affect a vibrating fork?
Light foam and bubbles are ignored because they add almost no mass. Heavy, drying buildup between the tines should be cleaned off during routine maintenance.
Can the LFV switch a pump directly?
Small loads can be driven from the PNP output (up to 250 mA). For motors, use the output to drive a contactor or feed a PLC input.
Which liquids can it detect?
Almost any liquid up to about 10,000 cSt viscosity — water, oils, fuels, solvents, milk, syrups and chemicals compatible with SS316.
Is calibration needed on site?
No. The fork compares against its own dry frequency, so it works out of the box for most liquids.
Do you supply Trumen with a GST invoice?
Yes. Every order ships with a GST invoice, and in-stock LFV switches dispatch the same day from Noida.
Get the Right Trumen LFV
Tell us the liquid, tank or pipe size, process connection and supply voltage. We will confirm the right LFV model and quote from stock.
Office Address
F412 (4th floor), Plot No-21, Arthamart, Techzone-4, Noida Extension, UP — 201318
By appointment only
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