What Are the Selection and Application of Tuning Fork Level Switch

Tuning fork level switch is a compact control switch dedicated to liquid level measurement. Compared with float level switches, proximity switches and other instruments, it has a higher reliability in detecting the liquid level. It is a liquid level measurement instrument that is very widely used in modern automated production. Besides, it can be seen in the water conservancy, chemical industry, environmental protection, electric power, food, medicine, and other industries, containers, tanks, and various pipeline level measurements.

Compared with the traditional tuning fork level switch, which does not distinguish between the measured objects and is used for both solids and liquids, the tuning fork level switch for counting is a specialized control instrument for liquid level measurement. It can provide more accurate and reliable liquid level measurement. To assist users in better understanding and selecting instruments that meet their working condition requirements for reliable liquid level measurement, this article takes the tuning fork level switch as an example and introduces its working principle and selection criteria.

What Are the Selection and Application of Tuning Fork Level Switch


The tuning fork level switch isn’t suitable for measuring levels in containers and tanks, but also for conduit level measurement. It’s especially suitable for environments with foam, bubbles, viscous liquids, and vibration interference, making it suitable for complex measurement scenarios. Also, it can measure liquids with a minimum density of up to 0.7g/cm³.

The working principle is designed based on the vibration principle of a cantilever beam and the design principle of detecting the change in vibration frequency when the fork body is immersed in the medium. It achieves fork body vibration drive and detection through the use of piezoelectric devices. Driven by piezoelectric ceramics, the tuning fork body vibrates at a certain mechanical resonance frequency. When in contact with the measured liquid, the resonant frequency of the fork body will be significantly reduced, resulting in a change in vibration frequency. This change is directly reflected in the output signal of the piezoelectric detection device, and then discriminated and outputted as a switching signal by the detection circuit based on the change in vibration frequency.

In the measurement of the low point, if the liquid medium is lower than the position of the fork body, the liquid medium and the fork body will be out of contact, and the instrument will produce an alarm signal. In measuring the high point, when the fork body contacts the liquid medium, the instrument will also generate an alarm signal. As for the actual application, whether the tuning fork level switch is installed at the high point or the low point, or at both high and low points, should depend on the specific needs of the operating site.



However, due to the significant variation in actual working conditions, different parameters are objectively required to tune the tuning fork level switch to match them. This involves the selection of the instrument. Generally speaking, the selection of the tuning fork level switch needs to focus on several aspects, including the physical and chemical properties of the measured medium, the temperature of the measured medium, the type of explosion-proofing, the probe length, and the installation method.

Properties of the Measured Medium

The properties of the medium have physical properties and chemical properties, so, in the selection, but also mainly to confirm the physical and chemical properties of the measured medium.

  • Confirm the physical properties of the measured medium

To achieve accurate measurement results, selection needs to confirm the physical properties of the liquid, such as the density of the size, and accordingly select the tuning fork level switch to match the density of the medium. The lowest measurable medium density can be measured as low as 0.7g/cm³.

  • Confirm the chemical properties of the measured medium

To ensure that the instrument can be reliably applied, in the selection, to confirm the chemical properties of the measured medium, such as whether the liquid is corrosive. And according to the strength of the measured medium corrosive, select the corresponding anticorrosive function of the tuning fork level switch, so as to avoid the instrument in contact with corrosive media for a long time corrosion occurs.

The Temperature of the Measured Medium

Because the fork of the tuning fork level switch needs to be in direct contact with the measured medium, different process temperatures need to be selected to match the tuning fork level switch. The normal temperature type tuning fork level switch has a process temperature range of 0 to 150 ℃, while the high-temperature type tuning fork level switch has a process temperature range of 150 to 200 ℃, which can be used for most industrial environment measurements.

High temperature Fork Level Switch

Explosion-proof Type and Explosion-Proof Class

Some industrial environments contain potentially flammable and explosive gases, etc., which are explosive hazards. Therefore, before selecting and purchasing the type, you should confirm whether the site has an explosion hazard to ensure a safe production environment and promote operational efficiency. If explosion-proof is required, the type of explosion-proof required and the explosion-proof level should be confirmed, such as whether it is intrinsically safe or explosion-proof, and what is the required explosion-proof level. Explosion-proof tuning fork level switches are available in both intrinsically safe and explosion-proof types. Users can choose the corresponding explosion-proof tuning fork level switches according to the requirements of the on-site environment.

Probe Length

The tuning fork level switch is a point contact measurement, after the installation position is determined, the probe length can be customised according to the insertion depth of the container, and the insertion depth is usually appropriate for the fork body to be able to completely contact the material.

Process Connection and Its Specifications

The process connection of field instrumentation generally has two kinds of threaded connection and flange connection, what kind of process connection is needed in actual application? For example, threaded or flanged, what specifications are needed? When purchasing and selecting, the selection should be made according to the field requirements.

Count for the tuning fork level switch is particularly suitable for narrow pipeline level measurement, to provide customers with threaded and flange and other process connections for users to choose.

Cable Inlet, Power Supply and Signal Output Method

Confirm the specifications of cable inlet, AC or DC power supply, relay or PNP signal output.

Due to varying working conditions, the parameters for the tuning fork level switch differ, necessitating careful communication between users and the factory to confirm the relevant parameters. This ensures the selection of cost-effective products that best suit the field’s requirements, thereby guaranteeing reliable measurements during product application.

Thread PTFE liner Fork Level Switch


  • Liquid storage tanks.

It can be used to monitor the level of liquid storage tanks, such as chemical plants, and petrochemical equipment in the tank. Through real-time monitoring of the level of liquid, you can judge whether the liquid in the tank is too full or too little, in order to avoid overflow or dry situation.

  • Sewage treatment.

In the sewage treatment system, it can be used to monitor the level of the sewage tank or sedimentation tank. When the level reaches a certain height, the switch will send out a signal to trigger the corresponding control action, such as starting the pumping station for drainage to maintain the normal operation of the sewage system.

  • Liquid Mixing Tank.

In the chemical production process, it is often necessary to mix several liquids. The tuning fork level switch can be used to monitor the liquid level in the liquid mixing tank to ensure that the mixing of liquids in the proportion is accurate. When the level reaches the set value, the switch will send a signal to control the feeding or discharging of the mixing tank to maintain the stability of the liquid in the mixing tank.

  • Drinking water supply.

In drinking water supply systems, it can be used to monitor the water level in a tank or tower. When the water level is too low, the switch will trigger the corresponding control action, such as automatically starting the water pump to ensure that the residents’ normal water demand is met.

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