Eddy current sensors are characterized by their simple structure, ease of non-contact continuous measurement, high sensitivity, and strong applicability. As a result, they have been widely used. Their applications can generally be categorized into the following four areas:

1. Displacement Measurement: By using displacement as a variable, eddy current sensors can be made to measure displacement, thickness, amplitude, vibration, rotational speed, etc. They can also function as proximity switches and counters.

2. Material Resistivity Measurement: By using the resistivity of materials as a variable, these sensors can measure temperature and differentiate between materials.

3. Magnetic Permeability Measurement: By using magnetic permeability as a variable, eddy current sensors can measure stress and hardness.

4. Combined Effect Measurement: Utilizing the combined effects of various variables, eddy current sensors can be used for flaw detection devices.

   An example of such an application is a device that uses a low-frequency transmission eddy current sensor to measure the thickness of metal materials. The eddy currents generated within the metal conductor create a counter magnetic field and consume some energy. These effects "reflect" back and can change the impedance of the original excitation coil, thereby enabling the measurement of the thickness of the metal material. To achieve a good reflection effect, the higher the excitation frequency, the shallower the penetration depth; hence, this type of eddy current sensor is used more frequently in practice. Additionally, if the excitation frequency is lowered, the penetration depth of the eddy currents increases, allowing for the creation of low-frequency transmission eddy current sensors.