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Multimeter testing: Before using a multimeter for testing, we first examine visually to check whether the protective tube is corroded or punctured, and whether there is any leakage. Then, we use the multimeter to check for continuity; the resistance of a modular thermocouple should generally be no more than 2 ohms, while that of a network cable-type thermocouple should generally be no more than 50 ohms. Generally, if it’s greater than 1K, it can be determined to be faulty. The above are only judgments based on ordinary thermocouples and explosion-proof thermocouples; when operating in high-temperature environments for extended periods, temperature drift can occur, and it is common for there to be a drift of 2–5 degrees at 1000 degrees. In accordance with relevant technical regulations, it is a standard measuring instrument subject to mandatory calibration; as it relates to energy conservation and safe production, it is generally required that such flow meters be sent to a flow meter calibration center for inspection after one year of use. Use a multimeter to measure the resistance value. If the resistance is above 100K, the component is faulty. To test a thermocouple using the multimeter’s ohm function, set the resistance setting, connect the two ends, and apply slight heat with a lighter. If the multimeter’s pointer moves significantly either up or down, it indicates that the component is functional; if the pointer does not move, then the component is damaged. The voltage across the terminals can be measured using the millivolt setting on a multimeter; if no voltage is detected, the device is damaged.