A variety of nuclear detection instruments have been developed by using the interaction phenomena between rays and matters such as, absorption, scattering, ionization and excitation of the measured substance. The ray passes through the measured substance and is absorbed and weakened. The ray intensity is detected by the detector, and then the corresponding processing is carried out to obtain the required physical quantity.

Nuclear density meter (radioactive densitometer, nuclear radiation densitometer or γ densitometer) is a kind of instrument for measuring the density of a substance based on the principle that the intensity of γ-rays changes with the density of the substance when γ-rays pass through the measured substance. Nuclear densitometer is widely used in food, paper making, chemical industry, oil, coal and tobacco.

The nuclear radiation thickness meter can be divided into two categories: one is to use the intensity change caused by the absorption of β, γ and other nuclear radiations penetrating the measured substance to measure the thickness of the measured substance, the other is to measure the ray intensity of the back-scattering, based on the principle of nuclear radiation back-scattering, and the scattering phenomenon when the ray passes through the material, when the scattering angle exceeds 90°, the back-scattering occurs, and the back-scattering intensity is related to the thickness of the substance, then the thickness of the measured material can be reflected.

Nuclear material level meter is also called γ-ray material level meter, which is an instrument for measuring the material level by using the blocking effect of material to γ-ray. The γ-ray material level meter is especially suitable for the measurement of material level under severe conditions such as high temperature, high pressure, high corrosion and high viscosity. The measured substance can be powder or granular solid or liquid. It is generally used in the case of two-phase interface, and is not applicable to multi-interface measurement.

According to the principle of industrial meters, BEIJING HAMAMATSU PHOTON TECHNIQUE INC. can provide scintillators, PMTs and scintillation detectors, to measure many important parameters such as thickness, density and material level.