ZRC-KX-YVP-2*1.5 Flame Retardant Shielded Extension Compensating Cable；

Section 1: Principle of Compensation Wires

Thermocouple compensating wires are conductors with thermoelectric properties similar to those of thermocouples within a certain temperature range. According to the thermocouple intermediate temperature rule, the total electromotive force value of the thermocouple temperature measurement circuit is only related to the temperatures of the hot and reference junctions, 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 using the compensating wire. Besides 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 enhance the flexibility of the circuit, making connections easier and more shielded against external interference; they can also reduce the cost of the measurement circuit.

II. Compensation Wire Classification

Extended and compensating types, with the extended type having an alloy wire nominal chemical composition identical to the thermocouple it is paired with, thus sharing the same electromotive force, denoted by "X" in the model. The compensating type has a different alloy wire nominal chemical composition, but within its operating temperature range, the electromotive force is nearly equal to the nominal value of the thermocouple's electromotive force, denoted by "C" in the model. In terms of compensation accuracy, there are standard and precision levels, where the precision level's post-compensation error is approximately half that of the standard level, commonly used in high-precision measurement applications. For example, S and R type compensation wires have a precision tolerance of ±2.5℃, while the standard tolerance is ±5.0℃; for K and N type compensation wires, the precision tolerance is ±1.5℃, and the standard tolerance is ±2.5℃. In the model, the standard level is not indicated, while the precision level is denoted by adding an "S". From the perspective of operating temperature, there are general-purpose and heat-resistant types, with general-purpose operating temperatures at 0 ~ 100℃ (some at 0 ~ 70℃), and heat-resistant operating temperatures at 0 ~ 200℃. Additionally, compensation wires can be categorized as single-core and multi-core (soft wire) based on the number of wire cores, and as ordinary or shielded types based on whether they have a shielding layer.

Section 3: Several Issues in Application

1. Matching Compensation Wires with Thermocouples: Various types of compensation wires can only be used with thermocouples of the same type number to avoid 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, Reference End for 0℃ Thermal EMF, at 100℃ 200℃ mV

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

When using compensation wires with a K scale in conjunction with thermocouples of an N scale, overcompensation will occur, showing a higher temperature reading; conversely, using N scale compensation wires with K scale thermocouples will result in undercompensation, leading to a lower temperature reading.

ZRC-KX-YVP-2*1.5 Flame-retardant Sheathed Extension Compensating Cable