There are three ways to measure nitrogen adsorption volume by 

　●Weight Method: Use high accurate balance to measure the increased weight of nitrogen adsorbed sample, and then calculate its volume. Its accuracy is determined by the balance, normally applicable not to small surface area testing.

　●Volume Method: In a closed system with known volume, put sample in, set a series of different nitrogen pressure, and calculate nitrogen adsorption volume according to state of equation of gas, e. g. the relationship between gas mass, temperature and pressure.

　The above two methods are called static methods. 

　●Dynamic Method: Also called continuous gas chromatography, it uses chromatography technique to measure nitrogen adsorption volume on sample surface in a continuous gas running passage. This method is simple and fast, good anti-disturb, applicable widely. JW series from JWGB all adopt this dynamic method.