Vibrating Tuning Fork Liquid Level Switches

Vibrating tuning fork devices for monitoring liquid level and activating switch contacts at predetermined liquid level thresholds.

A vibrating tuning fork liquid level switch is an instrument for monitoring the height of a liquid and tripping a relay contact switch or transmitting a solid state relay switch output when a maximum, minimum or intermediate level has been reached. The liquid level switch output can then be utilised by other instrumentation to open a valve, illuminate a warning lamp, activate an audible alarm, or switch on a pump.

Featured liquid level measurement products

LMK458 Marine Approved Hydrostatic Level Transmitter - Marine approved level transmitter with 4-20mA output for measuring level of contents inside ship ballast, fuel, liquid cargo or wastewater tanks
LMP307 Submersible Level Transmitter - Submersible level transmitter for measuring liquid level with a 4-20mA current loop or a 0-10V voltage output plus optional ATEX approval for intrinsically safe use in hazardous areas in ranges from 1mH2O up to 250mH2O. The LMP307 is suitable for use on potable water with no leaching, and can be supplied with a drinking water certificate according to DVGW and KTW.

Vibrating tuning fork liquid level switches are threshold contact trip devices which typically consist of a tuning fork which extends out from the switch housing.

In operation a piezoelectric oscillator is used to vibrate the tuning fork at its natural frequency for air.

A second piezoelectric device is used to pick-up the frequency of the vibrating tuning fork. When the liquid level rises and covers the tuning fork it will vibrate at a lower frequency.

This change in vibration frequency is used to detect when the required liquid level has been reached.

Featured liquid level measurement products

OEM sensor for diesel tank level measurement - Submersible hydrostatic level sensor for OEM integration in diesel fuel tanks. Low-power, 0.5 to 4.5V output.
LMK 858 Plastic Submersible Liquid Level Sensor with Removable Cable - Chemical resistant liquid level sensor with detachable signal cable for measuring quantity of aggressive media such acids and alkalis and sludge in tanks located outside of factory buildings.

A vibrating tuning fork liquid level switch makes direct contact with the liquid to be measured, and therefore material compatibility has to be a consideration.

Since there are no pressure sensitive components exposed to the inside of the tank it is possible to fit tuning fork level switches to sealed pressurised tanks.

Also, since there is no sensitive components immersed in the fluid it is possible to use them on higher temperature media that would not be tolerated by other types of liquid level switch.

Vibrating tuning fork liquid level switches are generally mounted through the top or side of the tank with the tuning fork protruding horizontally into the tank.

Featured liquid level measurement products

ATM/N Titanium Submersible Hydrostatic Pressure Transmitter - All Titanium submersible pressure transmitter for measuring the hydrostatic level of leachate, brackish water or sea water. Ranges from 1 up to 250mWC.
LMP305 Borehole Level Transmitter - Submersible stainless steel pressure transmitter ideal for geotechnical surveying with a 19mm diameter for measuring hydrostatic water level in bore-holes.

Advantages

Not affected by any surface disturbances such turbulence, foaming, vibration
High temperature fluid compatibility since no sensitive components make contact with the fluid
Small compact size
Sealed pressurised or evacuated vessels will not affect performance

Disadvantages

Thick or sticky media will leave a coating on the probe which will affect vibration frequency
Fouling can interfere with resonant frequency causing false switch activation
Tuning fork protruding into liquid causing obstruction, attracting fouling and hygienic cleanliness issues
High cost

Featured liquid level measurement products

External Mounted Tank Level Sensors - External mounted level sensors for installing on the outside of a liquid storage tank to measure level of tank contents.
Generator diesel tank height level sensor for 1 metre height - Prevent generator downtime and fuel theft with this easy-to-install diesel level sensor. 0.5 to 4.5Vdc output for seamless integration with MCUs.