Thermocouple type correct selection method

Choose the thermocouple used according to the temperature range, the required accuracy, atmosphere, the performance of the measured object, response time and the economic benefits and other comprehensive consideration.

a, the choice of measurement precision and temperature measurement range

in 1300 ~ 1800 ℃, using temperature requirement and high accuracy, generally choose B type thermocouple, required accuracy is not high, the atmosphere and allow tungsten-rhenium thermocouples are available, and higher than 1800 ℃ generally choose tungsten-rhenium thermocouples;

in 1000 ~ 1300 ℃ using temperature accuracy and higher available S type thermocouple and N type thermocouple;

under 1000 ℃ with K type thermocouple and N type thermocouple commonly;

below 400 ℃ in general use E type thermocouple;

250 ℃, and the negative temperature is generally measured in T thermocouple, T thermocouple during low temperature stability and high precision.

2, the choice of using atmosphere

S, type B, type K thermocouple is suitable for strong oxidation and weak reducing atmosphere in use;

J type and T type thermocouple is suitable for weak oxidizing and reducing atmosphere, if use air tightness better protection tube, the atmosphere is not too strict.

3, durability and thermal response options

wire diameter of thermocouple better durability, but some response is slow, the heat capacity of thermocouple, response is slow, measure the gradient of temperature, in the case of temperature control, temperature control is poor. Requirements for fast response time and has certain durability requirements, choose armored even more appropriate.

4, the nature of the measured object and the state's choice of thermocouple

motion object, vibration, temperature measurement requirements of high mechanical strength, high pressure vessel with chemical pollution of the atmosphere requires protecting tube, with electrical interference requirements under the condition of the insulation is quite high.

5, selection process

model & ndash; Index number & ndash; Explosion-proof grade & ndash; Precision grade & ndash; Installation of fixed form & ndash; Protecting tube material & ndash; Length or insert depth

product selection and ordering information:

1, when choosing and ordering, please specify the

2, product model,

no. 3, dividing

4, protection of pipe diameter and

5, protecting tube length L and a depth of

6, fixing device type

7, product actual measurement range

8, screw-type fixture type not marked with orders are fixed external thread M27 & times; 2 ( All the rest of the thread fixed type indicate)

9, because of its special user needs, and not in conformity with the above product model, need special products, please indicate your special technical requirements, to ( Or letter) Contact with my company about the responsibility department special orders.

10, the choice of different temperature thermocouple skills

thermocouple choice, should first according to the measured temperature limit and using the environment to select the thermocouple thermal electrode and protect casing, secondly according to the structure and installation feature of object to select the size of thermocouple.

thermocouple according to the structure form of different can be divided into: ordinary type industry, kai type, high functional entity type and special type thermocouple.

six, common ordinary industrial thermocouple have the following kinds:

( 1) Nickel chrome a constantan thermocouple are inexpensive metal thermocouple, it is extremely nickel-chromium alloy ( EP) , the negative is copper and nickel alloy ( EN） 。 Long-term use of temperature of 600 degrees, short-term use temperature of 800 degrees, the biggest characteristic is thermoelectric emfs rate, namely the highest agility, but susceptible to oxidation, index number is E.

（ 2) A copper constantan thermocouple is a cheap metal thermocouple that is extremely pure copper ( TP） And negative extremely constantan ( Copper and nickel) Alloy ( TN） 。 A thermocouple in general use in low temperature condition, temperature measurement range 200 ~ 300 ℃, the average sex that hot wire electrode, not disorderly, agility is good, price is low, index number is T. Kai fitting type thermocouple is the hot wire electrode in the insulation material of the metal casing, the combination is processed into the combination of flexible solid, again according to the required length truncation, its measurement end and reference end processing is made from kai type thermocouple. This kind of thermocouple can be done very fine is very long, in use can be bent, with measurement needs its wide temperature range, fast response speed, the heat capacity of small hot junction place, long service life. At the same time, its high mechanical strength, high pressure function, wide adaptability, around the big, install and use, then, is widely applied.

（ 3) Platinum germanium 10 & ndash; — Platinum thermocouple belong to precious metal thermocouple, contain the name of the anode containing germanium 10% of platinum germanium alloy ( SP） , very pure platinum (negative SN) 。 Long-term use of temperature 1300 ℃, short-term use temperature 1600 ℃. Strong anti-oxidation function, appropriate in oxidation, continuous use inert environment. Commonly used in high temperature measurement accuracy requirements, but the price is expensive, poor mechanical strength, small thermoelectric emfs, needs the display instrument with high agility, index number is S.

（ 4) Nickel chromium a nickel silicon thermocouple belong to cheap metal thermocouple, it is extremely nickel-chromium alloy containing 10% ( KP） , the negative is extremely containing silicon 3% nickel silicon alloy ( KN) And negative magnetic. Long-term use of temperature 1000 ℃, short-term use temperature 1200 ℃, thermoelectric potential 4 ~ 5 times larger than the S type thermocouple, excellent linearity, using a wide temperature range and is inexpensive metal thermocouple function one of the most not disorderly. Appropriate in oxidizing, inert environment of continuous use, cheap, error in about 7 ℃ or so. But its too hot electrode is not easy to do the average, easy oxidation, especially in low temperature condition, its not promiscuous sexual difference, index number is K.