Reply: The interior of the host adopts a modular design, and accessories such as carrier gas, hydrogen, standard gas and other gas cylinders and batteries are integrated inside the host. There is no external gas cylinder accessory box and battery accessory box, and no external connection is required. It is easy to use and portable. At the same time, it can prevent the safety hazard of gas leakage caused by external hydrogen, and the built-in standard gas can provide quality control requirements on site. Three kinds of gas cylinders are built in the back of the instrument, and are connected by threads, which can be installed and replaced without tools, which is very convenient.