Thermocouple Compensating Wire ZRC-KX-YVP1 Tin-Plated Shielded Temperature Measurement Wire；

I. Principle of Compensation Wires

A wire with thermoelectric properties similar to those of thermocouples within a certain temperature range is called a compensating wire for thermocouples. According to the middle temperature rule for thermocouples, the total electromotive force value of the thermocouple temperature measuring circuit is only related to the temperatures at the hot and reference ends, and is not affected by the change in intermediate temperature. Therefore, a compensating wire that matches the thermocouple material can be used to replace the expensive thermocouple material that needs to be extended, extending the reference end from the thermocouple terminal box to the instrument terminal, and compensating for the original reference end 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 measuring circuit, such as using multi-core wires or small-diameter compensating wires to increase the flexibility of the circuit, making connections easier and more susceptible to shielding external interference; they can also reduce the cost of the measuring circuit.

II. Compensation Wire Classification

Extended type and compensating type are categorized by principle. The nominal chemical composition of the alloy wire in the extended type is the same as the thermocouple it is paired with, thus the electromotive force 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 electromotive force is approximately equal to the nominal value of the electromotive force of the paired thermocouple, indicated by "C" in the model. In terms of compensating accuracy, there are general grade and precision grade. The error after compensation in the precision grade is roughly half that of the general grade, usually used in applications requiring high measurement accuracy. For example, compensating wires with S, R scales have a precision grade tolerance of ±2.5℃, and a general grade tolerance of ±5.0℃; for K, N scales, the precision grade tolerance is ±1.5℃, and the general grade tolerance is ±2.5℃. In the model, the general grade is not marked, while the precision grade is indicated by adding "S". By operating temperature, they are generally used and heat-resistant types, with general use operating temperature of 0 ~ 100℃ (some are 0 ~ 70℃); heat-resistant use operating temperature is 0 ~ 200℃. Additionally, they can be divided into single-core and multi-core (flexible) compensating wires based on the number of cores, and into standard and shielded compensating wires based on whether they have a shielding layer. There are also compensating wires specifically for explosion-proof circuits.

III. Several Issues in Application

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

Thermocouple Name | Thermocouple Type | Reference End for 0℃ | Thermoelectric Potential at 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—Cupronickel E 6.319 13.421 Iron—Cupronickel J 5.269 10.779 Copper—Cupronickel T 4.279 9.288

When using compensation wires with a K scale number paired with thermocouples of an N scale number, overcompensation occurs, resulting in a higher displayed temperature; conversely, using compensation wires of an N scale number with thermocouples of a K scale number leads to undercompensation, causing a lower displayed temperature.

Thermocouple Compensation Wire ZRC-KX-YVP1 Tin-Plated Shielded Thermometer Line