Types and functions of thermocouple compensation conductors
What type of thermocouple compensation wire and role?
First, why use compensation wire?
Because the temperature of the reference end of the thermocouple must be kept constant when using thermocouple temperature measurement, the measurement error introduced at the time of temperature measurement will be a large variable that will affect the accuracy of the temperature measurement. However, in the field use, the thermocouple reference end is often in the vicinity of the high temperature heat source, the thermocouple reference side by the heat source can not be stable, therefore must the thermocouple reference end to the temperature stable position; compensation wire with the same thermocouple Of the metal material, or in the specified temperature range (usually 0 ~ 100 ℃) within the thermoelectric properties (heat from the power) and the coupled thermocouple is the same, and is easy to obtain cheap base metal materials made in the temperature Can extend the role of thermocouple or thermocouple and instrumentation (such as electronic potentiometer) connecting wire. Therefore, the thermocouple in use to connect the compensation wire. But it does not eliminate the reference end temperature is not zero, so in use should be the reference end temperature should be corrected to 0 ℃.
Second, the use of compensation wire must pay attention to the following points:
1. All kinds of compensation wire can only be used with the corresponding type of thermocouple, that is to say a variety of thermocouple and supporting the use of compensation wire, in the specified temperature (such as 0 ~ 100 ℃) within the heat from the power must be consistent.
2. Compensation wire In connection with the thermocouple meter, two pairs of connection points to be at the same temperature, and positive and negative can not be wrong. Compensation wire is equivalent to a certain temperature (0 ~ 100 ℃) within the range of thermocouple, so its current is also from the reference side of the positive current to the negative, so when connected with the thermocouple, the positive pole of the compensation wire should be connected to the thermocouple Of the cathode, the negative should be connected to the negative of the thermocouple. If the polarity is reversed, not only lose the function of compensation wire, but will offset part of the thermocouple from the power, so that the instructions of the instrument temperature is low.
3. The temperature of the compensation wire and thermocouple connection point shall not exceed the specified temperature range.
4. According to the different requirements of the instrument used to select the compensation wire diameter. For example, with the moving coil instrument can be used to connect the compensation wire diameter thicker, so that the resistance value is smaller, so as not to affect the instrument's external resistance value.
5. Longer thermocouple, can be used multi-strand and thick compensation wire, in order to facilitate the installation and laying.
Third, the compensation wire should be due to different core alloy material is divided into extended and compensated two:
Extended compensation wire:
(Nickel-chromium-10-nickel-silicon-3), EX (nickel-chromium-10-copper-nickel 45), JX (iron-copper nickel 45), TX (copper- ).
Compensation type compensation wire:
There are SC and RC (copper - copper nickel 0.6), KC (copper - copper nickel 40), NC (iron - copper nickel) and so on.
Fourth, the use of extended or compensated compensation for the timing of the wire:
Extended:
Compensation line cold end of the environment is greater than 100 degrees or less than 0 degrees, in order to measure the accuracy, only the use of extended compensation wire, but the price is more expensive.
Compensation type:
The economy is cheap, but the cold side temperature must be in a relatively stable place.
Fifth, the compensation wire must have the characteristics:
1. Thermoelectric stability, electrical insulation performance, long service life.
2. Soft, flexible bending performance, easy to use.
3. Cladding material is stable and reliable, with a certain temperature and cold resistance.
