KX-H-YVP-2*1.0 Antijam Thermal Couple Wire with External Sheath Compensation Wire；

Section 1: Working Principle of Compensation Wires

Compensating wires, which have thermoelectric properties similar to thermocouple wires within a certain temperature range, are called compensating wires of thermocouples. According to the intermediate temperature rule of thermocouples, the total electromotive force value of the thermocouple temperature measurement circuit is only related to the temperatures of the hot junction and the reference junction, and is not affected by changes in the intermediate temperature. Therefore, compensating wires that match the thermocouple material can replace the expensive thermocouple material that needs to be extended, extending the reference junction from the thermocouple terminal box to the instrument terminal, and compensating for the original reference junction temperature with the compensating wire. In addition to reducing measurement errors, compensating wires offer the following advantages: they can improve the physical and mechanical properties of the thermocouple temperature measurement circuit, such as using multi-strand cores or small-diameter compensating wires can increase the flexibility of the circuit, making connections easier and more susceptible to shielding external interference; they can also reduce the cost of the measurement circuit.

II. Compensation Wire Classification

Extended and compensating types are differentiated in principle. The nominal chemical composition of the alloy wire in the extended type is the same as that of the thermocouple it is paired with, thus the electromotive force (EMF) is also the same, indicated by "X" in the model. The compensating type has a different nominal chemical composition from the thermocouple it is paired with, but within its operating temperature range, the EMF is nearly equal to the nominal EMF of the paired thermocouple, indicated by "C" in the model. Compensating accuracy is categorized into standard and precision levels, with the precision level having an error approximately half that of the standard level, commonly used in high-precision measurement applications. For example, compensation wires with S, R scales have a precision tolerance of ±2.5°C and a standard tolerance of ±5.0°C; for K, N scales, the precision tolerance is ±1.5°C and the standard tolerance is ±2.5°C. In the model, the standard level is not marked, while the precision level is indicated by adding an "S". Working temperatures are generally divided into general-purpose and heat-resistant types, with general-purpose ranging from 0 to 100°C (some up to 0 to 70°C), and heat-resistant ranging from 0 to 200°C. Additionally, compensation wires can be categorized by the number of cores (single-core or multicore, soft wire), by whether they have a shielding layer (standard or shielded type), and there are also compensation wires specifically designed for explosion-proof circuits.

III. Several Issues in Application

1. Matching Compensation Wires with Thermocouples: Compensation wires of various grades can only be used with thermocouples of the same grade; otherwise, there may be under-compensation or over-compensation. The compensating electromotive force values required for commonly used thermocouples at 100℃ and 200℃ are listed in Table 1: Table 1 - Compensating Electromotive Force Values of Common Thermocouples at 100℃ and 200℃

Thermocouple Name Thermocouple Type Number Reference End Potential at 0℃ mV 100℃ 200℃

Platinum Rhodium 10 - Platinum S 0.646 1.441 Platinum Rhodium 13 - Platinum R 0.647 1.469 Platinum Rhodium 30 - Platinum Rhodium 6 B 0.033 0.178 Nickel Chrome - Nickel Silicon K 4.096 8.138 Nickel Chrome Silicon - Nickel Silicon N 2.774 5.913

Nickel-Chromium—Nickel-Copper E 6.319 13.421 Iron—Nickel-Copper J 5.269 10.779 Copper—Nickel-Copper T 4.279 9.288

When using a compensation wire with a K degree of accuracy paired with a thermocouple of N degree accuracy, overcompensation will occur, resulting in a higher displayed temperature; conversely, using a compensation wire of N degree accuracy with a thermocouple of K degree accuracy will lead to undercompensation, showing a lower temperature.

KX-H-YVP-2*1.0 Antijam Thermocouple Wire with Outer Screening Compensation Wire