How to verify the quality of the electric heating tube we bought? The most intuitive method is: first wipe the surface of the electric heating tube, then switch on the AC 220V/380V power supply, dry it in the air, and then the surface becomes red. Turn off the power, after the heating tube is completely cooled, wipe it with a white napkin. There should be no black oxidizing powder on the white paper (not reacting with oxygen in the air), indicating that the heating tube is a high-quality electric heating tube.
