What should be paid attention to to prevent standard thermocouple pollution during thermocouple inspection? In the inspection of precious metal thermocouples, in order to avoid contamination of standard thermocouples, standard thermocouples must be covered with protective tubes. The protective tubes should be thin-walled and small-diameter protective tubes. Quartz or alumina tubes with a diameter of 8mm and a length of 400mm or a diameter of 6mm and a length of 400mm are usually used. The standard thermocouple is sheathed with a protective tube and the thermocouple to be inspected with the double-hole insulating tube is bundled with platinum wire, including the standard thermocouple The number of thermocouples per bundle does not exceed 5, and the clean platinum wire with a diameter of (0.1-0.3) mm at each measuring end is bundled together for 2 to 3 turns.

        When verifying a low-cost metal thermocouple, the standard thermocouple is covered with a protective tube, and the tested thermocouple covered with insulating ceramic beads is bundled with nickel-chromium wire into a circular bundle with a diameter not greater than 20 mm. When bundling, the measuring end of the thermocouple to be tested should be evenly distributed around the measuring end of the standard thermocouple for one week, and be on the same cross section as the standard thermocouple.