How to realize proportional gas supply for shielding gas during welding? Where to hang out?

Different welding methods use different gases, including single gas shielded welding (such as CO2 gas shielded welding) and mixed gas shielded welding (such as 95%-98% AR2+2%-5% O2 for stainless steel solid wire). Specifically, it can be mixed with a gas mixer (it can be mixed manually, but it is best to use a gas mixer for safety and accuracy).