Vibrating fork level Switch working Principle, application & advantages

Vibrating fork level switch

From acoustics to medical diagnostics, tuning forks are employed in a variety of disciplines. Quartz crystal tuning forks are used in timepieces as small tuning forks to measure time. The fork sensor’s two pointed tines begin vibrating at a set frequency when they make contact with any surface. The fork sensors are typically factory calibrated and set at a specific frequency depending on the type of industry. The length of the fork tines can affect the tuning fork’s pitch. Vibrating level switch is also known by many other names like fork level switch or tuning fork level switch, vibrating rod type level switch, vibration level switch etc.

vibrating fork level switch

History of tuning fork level switch

Since the 1970s, tuning fork level switches have been widely used in the sector. As an alternative to rotating paddle level switches, these were introduced. The market for point level switches is still dominated by vibrating fork level sensors because they have withstood the test of time. Vibrating forks have since developed into a quick and small level switch. Operation Without Calibration and Operational Life Expectancy is Relatively Long these factors are significantly responsible for the success and popularity of these level sensors:

Working principle of Vibrating fork level switch | Vibrating fork liquid level switch

A piezo crystal assembly, typically, drives a two-prong tuning fork to oscillate at its natural frequency in a tuning fork switch. Typically, a flange or threaded process connection is used to install the switch on the side or top of a tank such that the forks stick out into the tank.
The fork vibrates at its natural frequency when in the air, and the detector circuit keeps track of this vibration. The frequency of oscillation decreases when liquids cover the forks, which is recognised by the switch electronics, changing the output state of the level switch to operate an alarm, pump, or valve. The switch’s operating frequency was selected to minimise interference from natural plant vibration, which could result in erroneous switching.

vibrating fork liquid level switch

Vibrating fork level switch construction materials

The construction material is typically stainless steel, allowing usage in applications requiring high pressures and temperatures as well as the option of coated wet sides or exotic materials for corrosive applications.

Working Principle of Vibrating fork

The vibrating fork level sensor operates by constantly vibrating a tuning fork sensor at its natural frequency and sensing the change in frequency and amplitude when application media are present. The type of application medium determines how parameters are monitored.

1.Amplitude of vibration.
2.Frequency of operation.

1.Amplitude of vibration

The tuning fork level switch’s oscillation dampens as the material level rises and comes into contact with the tines of the vibrating fork. The outputs are altered by the onboard electronics when the amplitude falls below a predetermined threshold.

2.Frequency of operation

As the tuning fork level switch is covered with the liquid application media, the natural frequency of oscillation for the switch lowers. A tuning fork-type level switch’s natural frequency is used as the threshold frequency, which is tuned to match that frequency.

Switching hysteresis for Vibrating fork type level switch

Material flow or an agitator or stirrer inside the silos can also generate turbulence. This may result in changes to the tuning fork’s operating frequency and amplitude. A switching hysteresis is maintained around the switching point for accurate level sensing. This stops the switching point from being often toggled. Changing the sensitivity of a vibrating fork for solids may have an impact on the sensor’s hysteresis. Hysteresis margin typically shrinks as sensitivity rises. With an increase in tine length, a tuning fork’s inherent frequency rises.

Vibrating fork level switch for solid

The natural frequency and amplitude measurement of a vibrating tuning fork serves as the foundation for the vibrating fork level switch’s operation. Piezoelectric components are used to constantly vibrate a specifically formed tuning fork at its inherent frequency, and changes in amplitude in the presence of application media are monitored. The tines of the vibrating fork are forced apart from one another by the pressure given to the diaphragm, which returns to its original position when the pressure is released. The amplitude of oscillation of the vibrating fork level switch dampens or reduces when it is covered with the solid application media as the material level rises and comes into contact with the vibrating fork tines. The microprocessor detects the change in amplitude and decides whether to switch. The microprocessor notices the difference in amplitude, which results in a decision to switch. A vibrating fork-style level switch causes output adjustments when the amplitude falls below a predetermined threshold.

vibrating fork level switch for solid

Configuration of Vibrating fork level switch

Vibrating fork level switches can be set up to meet an application’s performance and installation needs. Different configurations are required depending on factors including process temperature, switching point length, installation area, and switching time. Tuning fork level switches are available in a variety of configurations. Housing, process connections, vibrating forks, finishes, and other important configuration options are only a few.

Application of Vibrating fork level switch

In cement manufacturing plant

In PET or PVC chips manufacturing industry

In packaging machines- Large production companies need quick automated packing equipment to fill packets with the right amount of material without failure or material loss. The increased need for industrial sites calls for level instruments with quick switching capabilities.

For applications that prevent overfilling, the dependable vibrating fork switch is suitable.

In the food, beverage, and pharmaceutical industries, point level liquid detection is used by fork level switch .

Advantages of vibrating fork level switch

Installing vibrating level switches is simple.
Without a medium, setup and commissioning are possible.
Unaffected by installation location, pressure, temperature, foam, viscosity, and particle size, reliable point level measurement.

Limitation of tuning fork level switch

For excessively viscous fluid, vibrating fork level switches are not recommended.
The forks get joined due to material buildup between them, which results in inaccurate level detection.

Name and model of vibrating tuning fork level switches

Some Name and model of vibrating tuning fork level switches are given bilow.

Vega manufactures the vibrating level switch. some of the model of vega vibrating level switches are as below


In the series of VEGAVIB they provide many model such as- VegaVib 61, vegavib 62, vegavib 63 vegavib S61 etc.


The series of VEGASWING provides many model such as- Vegaswing 51, Vegaswing 53, Vegaswing 61 , Vegaswing 63 etc.


VEGAWAVE series of vega provides many model such as- Vegawave 61, Vegawave 62, Vegawave 63 , Vegawave S61 etc.


Krohne also produce the vibrating fork type level swith. some of the most popular model of krohne are optiswitch3100, optiswitch3200, optiswitch3300, optiswitch4000, optiswitch5100, optiswitch5150, optiswitch5200, optiswitch5300 etc.


Rosemount is also there in the field of production of vibrating fork type level swith. some of the most popular model of rosemount in vibrating fork level switches  are rosemount 2130, rosemount 2120 level switch and rosemount 2140, rosemount 2160 level switch etc.

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