How to purchase qualified and suitable thermocouples

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When purchasing thermocouples, how can we find a temperature sensor that is suitable for our needs and meets the required standards? In fact, there are many ways and methods to evaluate thermocouples, and each method has its own characteristics. When purchasing thermocouples, we usually conduct on-site tests or use a multimeter for inspection. For testing with a multimeter: before doing so, we first examine visually 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 wire-type thermocouple should be no more than 50 ohms. Generally, if it’s greater than 1K, it can be determined to be broken. The above are only judgments based on ordinary thermocouples and explosion-proof thermocouples; when operating in high-temperature environments for an extended period, 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 with the multimeter’s ohm function, set the resistance setting, connect the two ends, and apply slight heat using 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 scale of a multimeter; if no voltage is detected, the device is damaged.