It should be noted that the damage and deterioration of some components of the gas meter and virtual welding do not have any signs on the surface, which can not be judged by naked eye observation, and it must be used by the instrument at this time. The instruments used are multimeters and oscilloscopes. It can be done with a multimeter. Check "on" or "off" and check the potential of each end. The oscilloscope can be used to check whether the operation is normal step by step. For example, whether the oscillator vibrates, whether it is normal, whether the amplifier is normal and so on.