Thermocouple compensation wires are crucial components that connect thermocouples to measuring instruments. Their primary function is to extend the cold end of the thermocouple to a temperature-stable environment, thereby ensuring accurate temperature measurements. The specifications of compensation wires must be determined comprehensively based on multiple factors, including the type of thermocouple, insulation and sheath materials, wire core specifications, and precision grades. Detailed explanations are provided below.

I. Core Dimensional Components of Specifications

The specifications of compensation wires are determined jointly by several key parameters, each of which directly influences their suitability and performance. These include the following main aspects:

Suitable thermocouple types: This is the core identifier for compensation wire specifications, which must precisely match the thermocouple's graduation number to ensure consistent thermoelectric properties. Commonly used graduation numbers include K 、 E 、 J 、 # Translated Text T 、 # Translated Text S 、 # Translation R 、 B Wait—different graduation numbers correspond to different thermoelectric potentials. - Temperature relationship.

Insulation and Sheath Materials: The material determines the compensation wire's environmental adaptability, including temperature resistance, corrosion resistance, and mechanical strength. Selection should be based on the specific conditions of the application scenario, such as temperature and medium.

Wire core specifications include the core material (with clear standards for the positive and negative materials of compensation wires) and the core cross-sectional area, which affects the wire's current-carrying capacity and signal transmission stability.

Accuracy Class: Reflects the thermoelectric potential deviation of compensation lead wires within the specified temperature range, directly affecting measurement accuracy. It is classified into Standard Grade and Precision Grade.

Structural Forms: Depending on wiring requirements and protection needs, there are various structures available, including single-strand, multi-strand, shielded, and unshielded types.

II. Common Specifications Classified by Thermocouple Type

Thermocouples of different graduation numbers correspond to dedicated compensation wire specifications. Below are detailed parameters for several types of compensation wires most widely used in industrial applications:

(1) K Type Thermocouple Compensation Lead Wire (Compatible with Temperature Scales) K , nickel-chromium - Nickel-silicon thermocouple)

(II) E Type Thermocouple Compensation Lead Wire (Compatible with Temperature Scales) E , nickel-chromium - Copper-Nickel Thermocouple

(III) J Type Thermocouple Compensation Lead Wire (Compatible with Temperature Scales) J ，  Iron - Copper-Nickel Thermocouple

(4) # Translated Text T Type Thermocouple Compensation Lead Wire (Compatible with Temperature Scales) # Translated Text T , copper - Copper-Nickel Thermocouple

(V) S/R Type Thermocouple Compensation Lead Wire (Compatible with Temperature Scales) S/R Platinum-rhodium 10 - Platinum / Platinum-rhodium 13 - Platinum thermocouple

III. Additional Key Specification Supplements

Shielding Layer Specifications: The shielding layer of shielded compensation wires is commonly made by braiding tinned copper wires, with typical braiding densities. 80%、90%。 80% Weaving density is suitable for general electromagnetic interference environments, such as factory workshops. 90% The weaving density is specifically designed for scenarios with strong electromagnetic interference, such as near motors or high-voltage equipment, effectively reducing the impact of electromagnetic interference on signals.

Specifications related to installation methods: Depending on the installation method, there are armored and non-armored types. Armored compensation wires (e.g., steel tape armor or steel wire armor) offer excellent mechanical protection and are suitable for scenarios where cables are prone to external damage, such as underground burial or cable trench installations. Non-armored types, on the other hand, are designed for indoor environments like cable trays or conduits, where protection is already provided.

Color Identification Standards: The color identification of compensation wires follows clear international standards. Typically, the positive pole is marked in red, while the negative pole's color varies depending on the thermocouple type. K Negative electrode type: blue E Negative electrode type: brown J When wiring, strictly follow the color-coded distinction between positive and negative terminals (e.g., black for negative). Connecting them in reverse can lead to measurement errors or even damage the instrument.

IV. Considerations for Specification Selection

Strictly match the graduation number: The graduation number of the compensation lead wire must be consistent with that of the thermocouple. K Type thermocouples must never be paired with E Type compensation lead wires must be used; otherwise, significant measurement errors may occur due to differences in thermoelectric properties.

Select Materials Based on the Environment: Prioritize materials suitable for high-temperature environments. FEP Silicone rubber material; suitable for use in humid and corrosive environments FEP 、 PFA Choose corrosion-resistant materials; select low-temperature-resistant options for cryogenic environments. PFA Material.

Balancing Precision and Cost: For general industrial control applications, a standard-grade option is sufficient to meet requirements; however, for precision measurement and laboratory settings, a precision-grade product is necessary. It's important to note that precision-grade wires typically come at a higher price compared to their standard-grade counterparts. 1.5-2 Twice.

Cross-sectional area adaptation distance: Transmission distance ≤ 50 meters Optional 0.5 mm² ； 50 meters to 100 meters Select and use 0.75 mm² ; > 100 meters It is recommended to select 1.0 mm² , to prevent signal attenuation caused by excessive line impedance.