At present, soft packaging products, such as bagged food, lithium battery, etc., have been widely used in the field of industry and people's livelihood. Due to the changes of biological, chemical and physical environment, gas will be produced in the soft packaging products, and the amount of gas produced is often related to the material properties in the soft packaging. For example, if the lithium battery in soft packaging is aged or heated, the electrolyte inside it will decompose, which may produce harmful or flammable gases, causing potential safety hazards to users; if the food in soft packaging is corrupt, it will produce methane, carbon dioxide and other gases, affecting food safety. Therefore, the measurement of the internal gas production of flexible packaging products is not only conducive to the quality control of flexible packaging products, but also an important means to ensure product safety.

At present, most of the methods to directly measure the internal gas content of soft packaging products are destructive measurement, that is, it is necessary to penetrate the packaging materials, release the internal gas, and then measure. The cost of this kind of destructive measurement is high, and it is a one-time measurement. It is impossible to observe the change of internal gas quantity of the same soft packaging product under different time and different biological, chemical and physical conditions.

In order to meet the needs of internal gas measurement of flexible packaging products, this instrument uses patented technology to measure the internal gas volume without damaging the external packaging of products. The instrument can be used to measure the internal gas content of lithium battery, bagged food and other products.

Another use of this instrument is to measure the coefficient of volume expansion of an object. Most of the existing measurements of the bulk expansion coefficient of materials are obtained from the linear expansion coefficient. Because the linear expansion coefficient of most materials is in the order of 10-6, the current method of measuring the linear expansion coefficient needs high-precision sensors, which can measure the small changes of the length of materials at different temperatures. When measuring, the material must be placed on the base, and the base itself will expand, and both the base and the material will vibrate, which makes it very difficult to measure small linear changes, resulting in the inaccuracy of the final volume expansion coefficient. It is convenient, fast and accurate to measure the coefficient of body expansion.