The β - ray thickness gauge mainly relies on two physical principles, penetration and backscatter, to achieve non-contact dynamic measurement in online detection of coatings/films. The core mechanism is based on the attenuation characteristics of the interaction between beta rays and matter, combined with the Beer Lambert law (J=J ₀ e ^ (- μ ρ t)) or Compton scattering effect, to calculate material thickness by detecting changes in radiation intensity.

Principle of Penetrating Measurement

Suitable for online monitoring of substrate and coating/film composite structures. After the particle stream emitted by a beta radiation source (such as Kr-85) penetrates the tested material, the detector receives the attenuated radiation intensity. Due to the correlation between the absorption coefficient (μ) and density (ρ) of beta particles in materials, when the substrate density is constant, the attenuation of radiation intensity (Δ I) is exponentially related to the thickness of the coating/film (t). For example, in the coating process of lithium battery electrode sheets, a beta ray thickness gauge can synchronously monitor the surface density of the substrate and the surface density of the electrode after drying. Real time conversion of thickness values (in the range of 0.1-2.2mm) can be achieved through standard sample calibration, with an accuracy of ± 0.1 μ m.

Principle of Backscatter Measurement

For thin coating (<2.5 μ m) or coating detection, after irradiating the sample with beta rays, some particles are reflected to the detector due to Compton scattering effect. The reflection intensity is related to the atomic number, density, and thickness of the coating, especially suitable for measuring precious metal coatings (such as gold and silver) or non-metallic coatings (such as aluminum oxide and zinc oxide). The ISO3543-81 standard stipulates that the atomic number difference between the substrate and the coating must be ≥ 5 to ensure accuracy. For example, the nickel plating layer on a copper substrate (atomic number difference of 28-7=21) can meet the detection conditions.

Technological advantages and industrial adaptability

Compared to X-ray thickness gauges, beta ray equipment is more suitable for online detection of extremely thin materials (such as metal strips below 0.8mm) due to its lower energy, and the radiation source has a lifespan of over 10 years, with lower maintenance costs. Its typical application scenarios include thickness closed-loop control in aluminum plate rolling, monitoring of rubber product coating amount, and thickness sorting of copper foil/aluminum foil for electronic components. The beta ray thickness gauge integrated with Huawei architecture software platform, launched in 2025, has been directly connected to MES system, supporting SPC statistical analysis and thickness data closed-loop control, significantly improving production efficiency.