The recommended length for thermocouple compensating leads is generally no more than 100 meters. The core reason for this is to avoid excessive lead resistance, which can lead to signal attenuation and an imbalance in the cold junction temperature gradient, thus affecting temperature measurement accuracy.
Specific adjustments should be made based on the application scenario: For typical industrial scenarios (such as normal temperature and short-to-medium distance transmission), a length of 50-100 meters is recommended. This range balances signal transmission stability with installation costs. For ultra-long distances (e.g., exceeding 100 meters), thicker core compensating leads (to reduce resistance) or shielded dedicated leads should be used, along with a low-input-impedance temperature measuring instrument to minimize signal loss. In high-temperature environments (>200℃) or scenarios with strong electromagnetic interference, the length should be further shortened (recommended ≤50 meters), and enhanced heat insulation and shielding should be implemented to prevent insulation aging or interference signal superposition.
Exceeding the specified length can easily lead to the following problems:
① Attenuation of the thermoelectric potential signal, resulting in lower measured values;
② Increased temperature gradient of the conductor itself, leading to increased cold junction compensation error;
③ Increased susceptibility to interference signals in strong electromagnetic environments, affecting data stability. In practical applications, adjustments should be made according to the instrument manual and the thermocouple calibration characteristics, with stable measured signals as the final standard.
