What are the types and functions of thermocouple compensation wires?

With the rapid development of industry, the use of thermocouples in production has become increasingly widespread. Thermocouples have become one of the most commonly used temperature detection components in industry, with characteristics such as high measurement accuracy, wide measurement scale, simple structure, and easy application. We have explored and analyzed products through various channels, providing a wide range of industry knowledge to a wide range of netizens.
Next, let me introduce the types and effects of thermocouple compensating wires?
1, Why use compensating wires?
It is necessary to maintain a stable temperature at the reference end of the thermocouple when using it for temperature measurement. Otherwise, the measurement error introduced during temperature measurement will be a major variable, which will affect the accuracy of the temperature measurement. However, in on-site applications, the reference end of the thermocouple is usually located near a high-temperature heat source, and the reference end of the thermocouple cannot be stabilized due to the influence of the heat source. Therefore, it is necessary to move the reference end of the thermocouple to a location with a relatively stable temperature; The compensating wire is made of the same metal material as the thermocouple, or has the same thermoelectric properties (heating power) as the thermocouple it is connected to within a regular temperature range (usually 0-100 ℃), and is made of readily available cheap metal materials. It can extend the effect of the thermocouple in temperature measurement or serve as a connecting wire between the thermocouple and instruments (such as electronic potentiometers). So, thermocouples need to be connected to compensating wires when in use. But it cannot eliminate the influence of non-zero reference temperature, so in application, the reference temperature should still be corrected to 0 ℃.

2, It is necessary to pay attention to the following points when using compensating wires:

1. Various compensating wires can only be used with corresponding types of thermocouples, which means that it is necessary for various thermocouples and the compensating wires used in conjunction to jointly generate electricity within a regular temperature range (such as 0-100 ℃).

When connecting the compensating wire to the thermocouple instrument, the two pairs of connection points should be at the same temperature and the positive and negative poles should not be connected incorrectly. The compensating wire is equivalent to a thermocouple within a certain temperature range (0-100 ℃), so its current also flows from the positive pole to the negative pole through the reference terminal. Therefore, when connected to the thermocouple, the positive pole of the compensating wire should be connected to the positive pole of the thermocouple, and the negative pole should be connected to the negative pole of the thermocouple. If the polarity is reversed, not only will it lose the function of compensating the wire, but it will also offset some of the heating power of the thermocouple, causing the instrument's indicated temperature to be lower.

3. The temperature of the compensating wire and thermocouple junction shall not exceed the temperature range specified for regular use.

4. The diameter of the compensating wire should be selected according to the different requirements of the equipped instrument. For example, the compensating wire connected to the dynamic coil instrument can be selected with a thicker wire diameter to reduce its resistance value, so as not to affect the external resistance value of the instrument.

5. For thermocouples with longer lines, multiple and thicker compensating wires can be used for easy installation and laying.

3, Compensatory wires should be divided into two types based on the different core wire alloy materials: extension type and compensation type

Extended compensating wires: NX (nickel chromium silicon nickel silicon magnesium), KX (nickel chromium 10 nickel silicon 3), EX (nickel chromium 10 copper nickel 45), JX (iron copper nickel 45), TX (copper copper nickel 45).

Compensation type compensation wires: including SC and RC (copper copper nickel 0.6), KC (copper copper nickel 40), NC (iron copper nickel), etc.

4, Opportunities for using extension or compensation type compensation wires:

Extended type:

When the environment where the cold end of the compensating wire is located is greater than 100 degrees or less than 0 degrees, in order to ensure measurement accuracy, an extended compensating wire can be used, but the price is relatively expensive.

Compensatory type: Economically inexpensive, but the cold end temperature must be in a relatively stable location.

5, The necessary features of compensating wires are:

1. Stable thermoelectric characteristics, good electrical insulation function, and long service life.

2. Soft and versatile, with good functionality and easy to use.

3. The coating material is stable and reliable, with certain temperature resistance and cold resistance functions.