K type thermocouple output of ac or dc millivolt voltage signal is belong to?

Thermocouple temperature measurement is the most widely used in the temperature of the device, his main characteristics is to kiss a wide range, stable performance, at the same time, simple structure, good dynamic response, more can far eastone - 4 20 ma electrical signals,

to facilitate automatic control and centralized control. Thermocouple temperature measurement principle is based on thermoelectric effect. Connect the two different conductor or semiconductor into closed loops, when the two contacts in temperature is not at the same time,

back to the road will produce thermoelectric potential, this kind of phenomenon called the thermoelectric effect, also known as the seebeck effect. There are two kinds of closed loop of thermoelectric potential of electric potential; The thermoelectric potential and contact potential. Thermoelectric potential means the same at both ends of the conductor for

temperature potential, as a result of the different different conductors with different electron density, so they produced by electric potential is not the same, the contact potential as its name implies is refers to the two different conductor in contact,

because their electron dense degree of different produce certain electronic diffusion, when they reach a certain potential, which is formed by the balance after the contact potential depends on the size of the two different conductor material properties and their temperature contact point.

the thermocouple of international application has a standard specification, the provisions on international thermocouple is divided into eight different degree, respectively B, R, S, K, N, E, J and T, its measuring temperature of minus 270 degrees Celsius, the minimum detectable

up to 1800 degrees Celsius, including B, R, S belong to platinum series thermocouple, because platinum are precious metals, so they are also known as precious metal thermocouple and the remaining few called cheap metal thermocouple.

thermocouple junction structure has two kinds, ordinary type and armoured. Ordinary thermocouples generally by the hot electrode, insulation tube, to protect casing and junction box parts, such as type and armoured thermocouple is the thermocouple wire,

the insulation material and metal protective casing combination after assembly, after stretching processing from a combination of a solid. But it takes a special electrical signal of thermocouple wires to pass, this kind of wire we called thermocouple compensating conductor.

different thermocouples require different compensation conductor, its main function is connected to the thermocouple, thermocouple reference end away from the power supply, so that the reference temperature stability. Compensation wire is divided into compensation type and extended type two kinds,

to extend the chemical composition of the wire and the compensation of thermocouple is the same, but in practice, to extend the type of wire is not used is the same as the thermocouple material of metal, usually use and thermocouple wires to replace with the same electron density.

the compensating conductor and thermocouple wires are generally not very clear, the positive connection of the thermocouple compensating conductor of the red line, while the cathode connecting the rest of the color. Most of the material compensating lead wires are commonly used copper nickel alloy.

temperature fluctuations don't call words, K type thermocouple output is dc, because of the steady state when the output voltage can be thought of without the change of the polarity. But under the below freezing into the electric potential is negative,

is higher than zero is positive. Personally think that if the temperature fluctuation, can be understood as communication ( Temperature fluctuation quantity) A dc component ( The average amount) The stack. As shown in the figure below: