K-type compensating wire is essentially a special type of wire that has the same thermoelectric characteristics as the matched K-type thermocouple within a certain temperature range. When using thermocouples for temperature measurement, it was originally necessary to directly connect the thermocouples to display instruments and other devices, but in practical scenarios, it is difficult to achieve due to factors such as long distance. At this point, use a compensating wire as an intermediate transition to extend the reference terminal of the thermocouple from the junction box to the instrument terminal. Because compensating wires can approximate the thermoelectric potential of thermocouples, the temperature at the original reference end can be compensated during this process to ensure measurement accuracy. By designing the materials, parameters, and layout of the wires reasonably, they can have specific resistance and inductance. These parameters can generate appropriate capacitance and inductance effects in transmission lines, thereby offsetting some voltage drops and power losses in the lines, effectively preventing voltage deviation from the normal range, ensuring the stability of signal transmission, and achieving compensation and regulation of line voltage.

Precautions for using K-type compensating wire:

1. Selection and matching

-Consistent with the thermocouple model: Compensation wires that match the K-type thermocouple used must be selected, and compensation wires of other models cannot be mixed. Because different models of thermocouples have different thermoelectric characteristic curves, mixing them can lead to increased measurement errors.

-Consider the usage environment: Select the appropriate compensation wire material and protection level based on factors such as temperature, humidity, and corrosiveness of the actual working environment. If in a humid environment, compensation wires with waterproof function should be selected; In highly corrosive environments, compensation wires made of corrosion-resistant special sheath materials are required.

2. Correct wiring

-Distinguish between positive and negative polarities: Connect the wires strictly according to the positive and negative markings on the compensation wire, ensuring that they are correctly connected to the corresponding terminals of the thermocouple and display instrument. Once reversed, it not only fails to compensate, but also introduces additional measurement errors, which are relatively large.

-Ensure a secure and reliable connection: The wiring terminals should be tightened to avoid looseness that may increase contact resistance and affect signal transmission. Welding, crimping, and other methods can be used to ensure good electrical connection, but care should be taken not to damage the insulation layer and internal core of the wire during operation.

3. Temperature control

-Avoid over temperature use: Compensation wires have a certain temperature range limit for use, and exceeding the specified temperature will cause changes in their thermoelectric characteristics, thereby affecting measurement accuracy. Therefore, it is necessary to ensure that the ambient temperature of the compensating wire is within its allowable range, especially the temperature at the connection point should not be too high.

-Reduce the impact of temperature gradient: Try to keep the two connection points of the compensating wire in the same temperature environment, or take insulation measures to reduce the temperature difference between the two points. Because temperature differences can generate additional heating potential, which can interfere with measurement results. The connection points can be placed in the same constant temperature device or wrapped with insulation material.

4. Anti interference measures

-Wiring away from interference sources: Compensation wires should be laid away from strong electromagnetic fields, power cables, and other interference sources. If crossing cannot be avoided, vertical crossing should also be used to reduce the length of parallel segments and minimize the possibility of electromagnetic induction coupling interference.

-Adopting a shielding structure and good grounding: For situations with strong electromagnetic interference, compensation wires with shielding layers are preferred. The shielding layer should be grounded at one end, and the grounding position should be far away from the grounding point of the power cable and other interference sources, generally at a distance of not less than 15cm, to prevent the interference current formed by the ground loop from affecting the signal. When multiple grounding points are connected, it is necessary to ensure that the potential difference between each grounding point is less than 0.1V.