Tone fork switch: The little master in industrial liquid level detection

In the vast system of industrial automation, there is a low-key yet crucial small component - the tuning fork switch. Perhaps you seldom hear of its name in your daily life, but in many fields such as chemical engineering, food, and pharmaceuticals, it is a powerful assistant that ensures the stable operation of production.

In simple terms, a tuning fork switch is a level detection instrument specifically designed for detecting liquid or material levels. From the appearance, it has components shaped like tuning forks, which is also the origin of its name. Don't underestimate this pair of tuning forks. They are the core of the entire switch. Just as a tuning fork in an instrument can produce a sound of a specific frequency when struck, the tuning fork in a tuning fork switch will also vibrate under specific conditions.

A Grand Revelation of the Working principle

(I) Vibration drive

The core component of the tuning fork switch is the pair of tuning forks, and the "unsung hero" that makes the tuning forks move is the built-in piezoelectric crystal. A piezoelectric crystal is like an energetic small motor. When an electric current passes through it, it undergoes deformation, and this deformation in turn excites the tuning fork to vibrate mechanically. Under normal circumstances, the vibration frequency of a tuning fork is usually around 1200Hz. This frequency is just like each person's unique fingerprint, which is the natural frequency when the tuning fork vibrates freely in the air.

(II) Frequency variation detection

When the working environment of the tuning fork changes, such as when it is immersed in a liquid, the situation is quite different. Liquid is like a mischievous little rascals, which will have a damping effect on the vibration of tuning forks. Imagine that when you wave your arms in the air and in the water, do you obviously feel that the resistance you encounter is greater in the water? The same is true for tuning forks in liquids. The damping they receive increases, resulting in a significant reduction in the vibration frequency. When the tuning fork is exposed to the air, without the "disturbance" of liquid, it will vibrate merrily within the originally set frequency range.

(III) Signal Conversion and Liquid Level Judgment

These changes in the vibration frequency of the tuning fork cannot be "unobtrusive"; they will be ingeniously converted into electrical signals. Inside the tuning fork switch, there is a precise electronic circuit, which is like a smart translator, specifically responsible for "translating" the changes in the vibration frequency of the tuning fork into electrical signals, and processing these electrical signals, such as amplification and filtering, to make the signals clearer and more stable, and then outputting them as switch signals. Such as common relay signals, PNP/NPN signals, or current signals that comply with the NAMUR standard (such as 8mA/3mA). The control system is like a commander. Based on the high and low states of these output signals, it can accurately determine whether the liquid has reached the set liquid level point, thereby achieving liquid level control or alarm functions. For instance, when the signal indicates that the vibration frequency of the tuning fork has decreased, it means that the tuning fork has come into contact with the liquid and the liquid level has reached the set position. The commander (control system) can then issue corresponding instructions, such as activating the alarm device or controlling the operation of related equipment.

There are really a lot of application scenarios

(I) Chemical industry

In the field of chemical engineering, the liquids contained in various reaction vessels and storage tanks are not ordinary ones, but rather "special guests" with characteristics such as corrosiveness and high viscosity. For instance, in a factory that produces sulfuric acid, the sulfuric acid in the reaction vessel is highly corrosive. the tuning fork switch is made of special corrosion-resistant materials, such as Hastelloy, which can work stably in such harsh environments, accurately detect the liquid level, and ensure the smooth progress of the reaction and the safety of the equipment. For instance, in some workshops that produce sticky products such as glue, high-viscosity materials pose a considerable challenge to liquid level detection. However, tuning fork switches are not affected by viscosity and can easily handle the situation, avoiding product quality issues and production accidents caused by improper liquid level control.

(II) Food and Pharmaceuticals

In the food and pharmaceutical industries, hygiene is a top priority. In the production process of beverages such as milk and fruit juice, hygienic tuning fork switches play a significant role. Its material meets food-grade safety standards, has a high surface finish, is not prone to dirt and bacteria residue, and can precisely control the liquid level to ensure the stable quality of each bottle of drink. In a pharmaceutical factory, from the preparation of the liquid medicine to the canning of the finished product, tuning fork switches strictly control the liquid level to ensure the quality and safety of the drugs. After all, the production of drugs cannot tolerate the slightest carelessness, and the precise control of the liquid level directly affects the dosage and therapeutic effect of the drugs.

(III) Sewage Treatment

The sewage treatment plant is the "cleaner" of the city, and the tuning fork switch is a capable assistant among them. Whether it is the turbid sewage at the water inlet, the mixed liquid in the sedimentation tank during the treatment process, or even the sludge containing various particles, the tuning fork switch can accurately detect the liquid level. By reasonably controlling the liquid level, the sewage treatment equipment can operate efficiently, ensuring that the sewage is properly treated and discharged up to standard, thus safeguarding our water environment.

The unique advantages are extremely powerful

the tuning fork switch can shine in many fields, which is inseparable from its own unique advantages. It is not affected by the properties of the medium. Whether it is density, viscosity, conductivity or dielectric constant, none of them will interfere with its operation. It can be applied to various liquids, slurries, and even medium-density solid powders or particles that can flow freely. In terms of precision, the tuning fork switch also performs well. It adopts the principle of mechanical vibration, with stable signals that are not easily disturbed by the outside world and high measurement accuracy. In terms of installation and maintenance, it is also very worry-free. It has a simple structure and does not require complex calibration. It can be directly installed on the side wall or top of the container, and there is no need for frequent maintenance in the later stage, saving a lot of human and time costs for enterprises.