The S-type compensation wire has two advantages.

Enhancing the physical and mechanical properties of thermocouple temperature measurement lines, using multi-strand cores or small-diameter compensating wires can increase the flexibility of the lines, facilitate wiring, and also adjust line resistance or shield external interference.

2. Reducing the cost of measurement circuitry, using compensating cables can save a significant amount of thermocouple material, especially when using precious metal thermocouples, making the economic benefits even more pronounced when the thermocouple and measuring device are far apart.

The nominal chemical composition of the S-type compensation wire alloy wire and the nominal electromotive force are identical to those of the thermocouple used. It is indicated by the letter 'X' appended after the thermocouple's grade number.

S-shaped Compensation Wire Precautions

1. Various S-type compensation wires are only compatible with the corresponding S-type thermocouples, meaning that the S-type thermocouple and the accompanying compensation wire must exhibit consistent thermal electromotive force within the specified temperature range.

When connecting to an S-type thermocouple, both pairs of connection points must be at the same temperature, and the positive and negative poles cannot be connected incorrectly. The compensation wire is equivalent to an S-type thermocouple within a certain temperature range, so its current flows from the positive pole to the reference end and then to the negative pole. Therefore, when connecting to an S-type thermocouple, the positive pole of the compensation wire should be connected to the positive pole of the S-type thermocouple, and the negative pole should be connected to the negative pole of the S-type thermocouple. If the polarity is reversed, it not only loses the function of the compensation wire but also cancels out part of the thermal electromotive force of the S-type thermocouple, causing the instrument's indicated temperature to be lower.

Compensation wires and S-type thermocouple connection points must not exceed the specified temperature range for use.

4. Select the wire diameter of the compensating cable based on the specific requirements of the instrument. For instance, when connecting to an electrodynamic instrument, a thicker wire diameter can be chosen to reduce its resistance value, ensuring it does not affect the external resistance of the instrument.

5. For longer S-shaped thermocouples, multi-strand and thicker compensation wires can be used for easier installation and laying.