Choosing a gas porosity measuring instrument requires comprehensive consideration from four dimensions: analysis requirements, technical principles, core parameters, and industry adaptability. The following is a specific selection guide:

1、 Clearly analyze requirements

Measurement object: Determine whether it is rock, soil, ceramics, or biological materials. The pore structure of different materials varies greatly, and an appropriate measurement principle needs to be selected. For example, rock measurement requires high pressure (such as 0.7 MPa) to penetrate dense pores, while biomaterials require physiological environment simulation.

Measurement range: Select the instrument based on the pore size. Micro porous materials (pore size<2nm) require ultra-low pressure (P/P ₀ ≤ 10 ⁻⁷) and high-resolution sensors (such as 1.6 × 10 ⁻⁶ Pa), mesoporous materials (2-50nm) require standard BET method, and macroporous materials (>50nm) can use gas expansion method.

Accuracy requirement: Scientific research level measurement requires an accuracy of ≤± 2%, while industrial quality inspection can be relaxed to ± 0.5%. For example, the porosity error of the catalyst support needs to be controlled within 1%, otherwise it will affect the reaction efficiency.

2、 Select technical principles

Gas expansion method (Boyle's law): applicable to hard materials such as rocks and soils, calculating porosity by measuring the equilibrium pressure of gas after isothermal expansion. For example, the laboratory of China University of Mining and Technology uses this principle to test samples with a core diameter of 50mm and a length of 0-100mm.

Gas adsorption method (BET theory): used for nanomaterials, ceramics, etc., to calculate the specific surface area and pore size distribution through the adsorption desorption behavior of adsorbate gases (such as N ₂, Ar) in the pores. For example, Beijing Jingwei Gaobo's static volumetric instrument can measure pore sizes ranging from 0.7-400nm.

3、 Core parameter selection

Measurement accuracy: High precision pressure sensors (such as 0.2% accuracy) and digital display systems are preferred to reduce human reading errors.

Sample adaptability: Confirm whether the instrument can handle samples of different sizes, such as 25mm core or powder samples, and support simultaneous testing of multiple samples (such as 1-4 samples).

Automation level: Fully automatic instruments can achieve the entire process of degassing, adsorption, and data calculation, reducing human intervention and suitable for batch testing.

4、 Industry adaptability

Geology and Energy: High pressure (0.7MPa) and helium/nitrogen medium are required to measure the porosity of reservoir rocks to evaluate oil and gas reserves.

Materials Science: Requires ultra-low pressure and nanoscale resolution to measure the mesoporous structure of battery electrode materials (such as graphite).

Biomedical: requires physiological environment simulation and 3D printed scaffold porosity analysis to ensure cell growth efficiency.