Several easily overlooked points about platinum-rhodium thermocouples
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The last edit to this post was made by tiandiyi*an on 2017-12-26 at 09:02. 1. Platinum-rhodium thermocouple wires The cleanliness of the wires in a platinum-rhodium thermocouple determines its measurement accuracy. If the filaments become contaminated, turn black, or oxidize, their accuracy becomes highly questionable. Next is the length of the thermocouple wire; in fact, this is specified in the inspection requirements for thermocouples – the length of the thermocouple wire must not exceed a certain limit. Because the length of the thermocouple wire is insufficient and it is too close to the temperature-sensing element, the measurement error increases. 2. Bendability of platinum-rhodium thermocouples The wires of platinum-rhodium thermocouples are thin and soft, so they tend to bend easily. If a thermocouple bent with twisted wire is used for measurement, errors are bound to occur in the results. Although the thermocouples are checked every time to ensure they are in optimal condition, even professionals can overlook certain things. I wonder if you have encountered such cases?
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Platinum-rhodium thermocouples are quite delicate, with thin and soft wires, and require careful protection.
Why is it said that there are measurement errors when bending filaments? What’s the logic? As long as the two pairs of wires do not touch each other, no measurement error will occur regardless of how much they are bent; this is probably determined by the principle of thermocouple measurement ； Otherwise, it’s impossible to keep a fine and soft platinum-rhodium thermocouple from bending.