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technical article
Common sense for armored thermocouples
2012-1-25 18:16:51

作为温度测量传感器,通常与温度变送器、调节器及显示仪表等配套使用,组成过程控制系统,用以直接测量或控制各种生产过程中0-1800℃范围内的流 As a temperature measurement sensor, armored thermocouples are usually used together with temperature transmitters, regulators and display instruments to form a process control system to directly measure or control the flow in the range of 0-1800 ° C in various production processes.

Temperature of solids, steam and gaseous media, and solid surfaces. The armored thermocouple has many advantages such as bending, high voltage resistance, fast thermal response time, and ruggedness. It is the same as the industrial assembled thermocouple.

Sensors, usually used with display instruments, recording instruments and electronic regulators

Single-point and multi-point armored thermocouples are a new generation of products carefully designed and manufactured by our company and in compliance with International Electrotechnical Commission (IEC) standards.

Meter dedicated sensor. When using this product, users need to provide their own external protective tubes, otherwise they can only measure atmospheric pressure and non-corrosive media.


有多支多点铠装热电偶和单支多点铠装热电偶两种。 There are two types of multi-point armored thermocouples, multi-point armored thermocouples and single multi-point armored thermocouples. Single branch multi-point armored thermocouples are produced by introducing advanced foreign technology for the company. The product is assembled in a single outer tube

The insulated thermocouple is armored, and the outer tube of the entire product is drawn to the outer diameter required by the user through drawing and other processes. The outer diameter of the product is usually Ф6-Ф8mm. When using this product, users need to prepare their own external protective tube, otherwise they can only measure atmospheric pressure

And non-corrosive media; the product must not be sharply bent to prevent damage to the internal armor.


principle


The working principle of armored thermocouples is that two ends of conductors of two different components are welded to form a loop. The direct temperature measurement end is called the working end, and the terminal end is called the cold end, also called the reference end. When there is a temperature difference between the working end and the reference end, it will

Generate a thermal current in the circuit, connect the display instrument, and the instrument will indicate the corresponding temperature value of the thermoelectromotive force generated by the thermocouple. 的热电动势将随着测量端温度升高而增长,热电动势 The thermoelectromotive force of the armored thermocouple will increase as the temperature of the measurement terminal increases.

The size is only related to the material of the thermocouple conductor and the temperature difference between the two ends, and has nothing to do with the length and diameter of the thermal electrode. The structural principle of the armored thermocouple is that it is protected by a conductor, high-insulation magnesium oxide, and a 1Cr18Ni9Ti stainless steel jacket.

It has been drawn in one piece several times. Armored thermocouple products are mainly composed of junction boxes, terminal blocks and armored thermal resistors, and are equipped with various mounting fixtures. There are two types of insulation and shell type.

Basic technical indicators

category


(Codename)


Index number

Outer diameter of casing (d)


Common temperature (℃)


Maximum use temperature (℃)

Allowable deviation △ t



Temperature measurement range (℃)


Tolerance value

Nickel chromium—constantan


WREK

E

≥φ 3


600


700


0 ~ 700

± 2.5 ℃ or


± 0.75% t

Ni-Cr-Ni-Si


WRNK


K


≥φ 3


800


950


0 ~ 900

± 2.5 ℃ or

± 0.75% t



Copper—Constantan

WRCK

T


≥φ 3


350


400


<-200


Unspecified

-40 ~ 350

± 1 ℃ or


± 0.75% t

Note: 1. t is the absolute value of the measured temperature

2.T type indexing products need to negotiate and order with the factory


Thermal response time

When there is a step change in temperature, the time taken for the thermocouple output to change to 50% of the step change is called the thermal response

The response time is represented by τ0.5.

Insulation resistance

When the ambient air temperature is 20 ± 1.5 ℃ and the relative humidity is not more than 80%, the insulated wire and jacket tube of the insulated armored thermocouple

The insulation resistance value between them should meet the requirements of the following table.

Even wire diameter (mm)


Test voltage (V-DC)


Insulation resistance (MΩ.m)

1.5


50 ± 10%


≥ 1000



> 1.5

500 ± 10%


≥ 1000


Flexibility

The bendable radius is not less than 5 times its outer diameter.


Thermal response time

Thermal response time

τ 0.5 seconds


Casing diameter


(Mm)


Shell type

Insulated

3.0
0.6
1.2

4.0
0.8
2.5

5.0
1.2
4.0

6.0
2.0
6.0

8.0
4.0
8.0


Outer diameter and nominal length standard specifications

Outer diameter d (mm)

φ 8
φ 6
φ 5
φ 4
φ 3

50
50
50
50
50

75
75
75
75
75

100
100
100
100
100

150
150
150
150
150

200
200
200
200
200

250
250
250
250
250

300
300
300
300
300

400
400
400
400
400

500
500
500
500
500

750
750
750
750
750

1000
1000
1000
1000
1000

1250
1250
1250
1250

1500
1500
1500
1500

2000
2000
2000
2000


2500
2500
2500


3000
3000
3000


4000
4000
4000



5000
5000



7500
7500



10000
10000




15000

Note: 1. The nominal total length L of the ¢ 3 insulated armored thermocouple shall not be greater than 10000mm.


2. For products with an outer diameter d ≤ ¢ 5mm and a splash-proof or waterproof junction box, users should pay attention to the installation of the thermocouple when the exposed part of the device must be equipped with auxiliary supports such as brackets to increase rigidity and ensure ruggedness to prevent wiring Box back and forth

Shake and damage the thermocouple