A vibrating fork is a type of level switch that often comes as part of an application because it can also be used for density measurement. Its name comes from a fork-like sensor in the bottom, which works on a principle similar to tuning forks.

How does a vibrating fork work?

Vibrating forks are commonly known as a simple point level detection device. However, some other applications also use it as a component.

Vibrating forks work on similar principles to tuning forks. They were invented by Endress+Hauser in 1967. The device has two-prong forks, and its forks are oscillating at its natural frequency because of a built-in piezo-crystal.

Liquipoint T FTW31 Conductive rod probe for multipoint detection for up to 5 switch points

We can install the vibrating forks on the top of a tank, or even on the pipes. When there is contact only with air, the two-prong fork will oscillate at its natural frequency, and the transmitter will continuously monitor this oscillation.

As soon as the product cover the forks, the frequency of oscillation will change, dropping the oscillation. The transmitter will detect the change and translate this information into a switch output. Then, one can turn the equipment on and off to avoid problems.

To know about level transmitter calibration, you can read our article here

Vibrating fork applications

Vibrating forks can be used in any application that calls for a level switch but they also have their particular use cases.

Vibrating forks for level detection

The vibrating fork’s primary application is point level detection. And unlike many people may think, we can install the device in different places, not just on top or on the side of the tank. In fact, the ideal position of the device depends on the application: we can implement the forks to protect the overfill or to indicate low level. Vibrating forks are also commonly used in rainwater tanks.

If we want to detect high level, we have to install  vibrating forks on the top or side of the tank. However, if we want to detect low level, we need to have forks at the bottom or side of the reservoir as well. We can make both applications and can have different level detection, such as high level, or high-high level. The extension of the vibrating forks will be different, and in that case, one should install them on the top.

Vibrating forks for full pipe detection

We can also use this device to detect whether your pipe is full or not. Why should we install a vibrating fork for full pipe detection? For example to protect a pump from running without any material in it.

Density measurement using a vibrating fork

If we have a density measurement application, there are options on the market combining the vibrating forks, temperature, and pressure for density measurement. This is a particular application, but there are exciting possibilities with vibrating forks.

We can also find a solution from Endress+Hauser with their vibronic measurement density computer FML621.

To know about level switches, you can read our article on the working principle of level switch


The working principle is not complicated at all, but the vibrating forks are an important part of level measurement. If we need to protect a tank, pipe, or even a density measurement, vibrating forks can be a good solution.

If you need help choosing the right level switch for your application, take a look at our new level smart assistant.

To know more about vibrating fork and level switches, you can get in touch with our engineers and we will be happy to help.

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