ColdJunctionKomensation

ColdJunctionKomensation, often written as cold-junction compensation (CJC), is a method used in thermometry to account for the temperature at the reference junction of a thermocouple. It ensures that the electrical signal reflects the temperature of the measurement junction rather than the unknown temperature at the connection point to the measurement instrument.

Thermocouples produce a voltage that is proportional to the temperature difference between the measurement (hot) junction and the reference (cold) junction. To determine the absolute temperature at the measurement junction, the temperature at the reference junction must be known and incorporated into the calculation.

Implementation ranges from simple to sophisticated. Traditionally, CJC was achieved by keeping the reference junction at a known fixed temperature, such as 0°C with an ice bath or a calibrated block. Modern instrumentation, however, measures the reference junction temperature with an additional sensor (thermistor, RTD, or integrated sensor) and computes a compensation value that is added to the thermocouple emf, either in analog circuitry or in software. The relationship between emf and temperature is non-linear and depends on the thermocouple type (for example, K, J, or T), so compensation relies on standard temperature-to-voltage mappings (ITS-90 or NIST-compatible data).

Accuracy considerations include the sensor’s precision, calibration, and drift, as well as potential errors from self-heating, junction gradients, and wiring. CJC is essential for reliable thermocouple measurements in industrial controls, laboratory instrumentation, and process monitoring.