Some standard content:
UDC. 621.315.32 536.516
National Standard of the People's Republic of China
GB/T4989—94
Extension and compensating cables for thermocouples
1994-12-22
State Bureau of Technical Supervision
Implementation on 1995-10-01
National Standard of the People's Republic of China
Extension and compensating cables for thermocouples
GB/T4989—94
Replaces GB4989—85
This standard equivalently adopts the main technical indicators of IEC Publication 584-3(1989) "Thermocouples: Part 3 - Tolerances and coloring marking system for extension and compensating cables".
1 Subject content and scope of application
This standard specifies product classification, technical requirements, test methods, inspection rules, marking, packaging, etc. This standard applies to compensation wires (hereinafter referred to as compensation wires) used with thermocouples with graduation numbers S, R, K, N, E, J and T. The insulation layer and sheath of the compensation wire are mainly made of polyvinyl chloride, alkali-free glass fiber and polytetrafluoroethylene. For other materials, if they can meet the technical requirements of this standard, they can also be used.
2 Reference standards
GB2614
Nickel-chromium-nickel-silicon thermocouple wire and graduation table
Batch inspection counting sampling procedure and sampling table (applicable to inspection of continuous batches)GB 2828
GB2829
Periodic inspection counting sampling procedure and sampling table (applicable to inspection of production process stability)Copper-copper-nickel (Constantan) thermocouple wire and graduation tableGB2903
GB 2951. 2
GB 2951.3
GB 2951. 4
GB 2951. 5
GB 2951. 6
GB 2951.7
Measurement method for insulation thickness of wire and cable
Measurement method for sheath thickness
Wire and cable
Wire and cable
Wire and cable
Wire and cable
Wire and cable
Outer diameter measurement method
Test method for mechanical properties of insulation
Test method for mechanical properties of sheath
Air box heat aging test method
GB 2951.12E
Low temperature winding test method for wire and cable
GB3772
GB 4993
Platinum 10-platinum thermocouple wire and indexing table
Nickel-chromium-copper-nickel (Constantan) thermocouple wire and indexing table GB4994 Iron-copper-nickel (Constantan) thermocouple wire and indexing table ZBN05004 Nickel-chromium-silicon-nickel-silicon thermocouple wire and indexing table 3 Terms and symbols
3.1 Terms
3.1.1 Extension and compensating cables for thermocouples A pair of wires with an insulating layer that have the same nominal value of the thermoelectric electromotive force as the matched thermocouple within a certain temperature range (including room temperature) and are used to connect thermocouples and measuring devices to compensate for the errors caused by temperature changes at the connection between them and the thermocouple. Compensating cables are divided into two types: extension type and compensating type. Approved by the State Administration of Technical Supervision on December 22, 1994 and implemented on October 1, 1995.
3.1.2Extension cables
extension cables
GB/T 4989—94
Extension cables are also called extension compensation cables. The nominal chemical composition and nominal value of thermoelectric emf of their alloy wires are the same as those of the thermocouple wires. They are indicated by the letter "X" added after the thermocouple graduation number, for example "EX". 3.1.3Compensating cablesCompensating cables are also called compensating compensation cables. The nominal chemical composition of their alloy wires is different from that of the thermocouple wires. However, their thermoelectric emf values are the same as those of the thermocouples at 0-100℃ or 0-200℃. They are indicated by the letter "C" added after the thermocouple graduation number, for example "KC". Different alloy wires can be used for thermocouples of the same model (grading number) and are distinguished by additional letters, for example KCA and KCB.
3.1.4 Tolerance tolerance
The tolerance of the compensation wire for thermocouples is the maximum additional deviation caused by the introduction of extended compensation wire or compensation compensation wire into the measurement system. The value is expressed in microvolts. 3.2 Symbols
indicates compensation wire with precision grade thermoelectric characteristic difference; indicates general compensation wire;
H-— indicates heat-resistant compensation wire;
R— indicates multi-strand compensation wire;
P— indicates compensation wire with shielding layer;
--polyvinyl chloride material (PVC);
F--polytetrafluoroethylene material;
B—alkali-free glass fiber material. ||t t||4 Product classification
4.1 Product variety
The product variety and product model of the compensation conductor are shown in Table 1. Table 1
Product name
Copper-copper inlaid 0.6 compensation conductor
Iron-copper nickel 22 compensation conductor
Copper-copper nickel 40 compensation conductor
Ni-chromium 10-nickel silicon 3 extension conductor
Iron-copper nickel 18 compensation conductor
Cr14 silicon-silicon inlaid extension conductor
Ni-chromium 10-copper inlaid 45 extension conductor
Iron-copper nickel 45 extension conductor
Copper-copper nickel 45 extension conductor
4.2 Product specifications
SC or RC
Matched thermocouple
Platinum 10-platinum thermocouple
Platinum 13-platinum thermocouple
Nickel-chromium-nickel-silicon thermocouple
Nickel-chromium-silicon-nickel-silicon thermocouple
Nickel-chromium-copper-nickel thermocouple
Iron-steel-nickel thermocouple
Copper-Kang steel thermocouple
Thermocouple graduation number
GB/T 4989—94
The core type, number of core strands, nominal core cross section and alloy wire diameter of the compensating conductor are shown in Table 2. 4.3 Product grade and usage classification
Compensating conductors are divided into precision grade and ordinary grade according to the different tolerances of thermoelectric characteristics. They are divided into general use and heat-resistant use according to the use temperature range. The classification and classification are specified in the technical requirements. 4.4 Product structure type
4.4.1 The core type of the compensating conductor is divided into single-strand core and multi-strand core (soft wire). The number of core strands is shown in Table 2. Table 2
Core type
Single-strand core
Multi-strand core
(soft wire)
4.4.2 Insulation layer, sheath, shielding layer
Nominal core cross section
The structure of the compensating conductor is generally composed of an insulation layer, a sheath or a shielding layer. 4.4.2.1 Insulation layer
The insulation layer of the general compensation conductor is mainly made of polyvinyl chloride. Number of core strands
Single wire diameter
The insulation layer of the heat-resistant compensation conductor is mainly made of polytetrafluoroethylene. If the heat resistance performance meets the technical requirements of this standard, other materials such as high-temperature rubber insulation are allowed. 4.4.2.2 Sheath
The sheath of the general compensation conductor is mainly made of polyvinyl chloride. The sheath of the heat-resistant compensation conductor is mainly made of polytetrafluoroethylene or alkali-free glass fiber. The sheath made of alkali-free glass fiber must be coated with silicone paint or sintered with polytetrafluoroethylene dispersion. If the heat resistance performance meets the technical requirements of this standard, other materials such as high-temperature rubber are allowed.
4.4.2.3 Shielding layer
It is braided with tinned copper wire or galvanized steel wire or wrapped with composite aluminum (or copper) tape. 4.5 Product code
Compensation wire product code, use temperature range, insulation layer and sheath main material are shown in Table 3. Thermocouple graduation number
Compensation wire model
SC or RC
GB/T 4989—94
KCA-GS
KCA-HS
KCB-GS
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
Insulation layer materials
and sheath materials||tt ||Use temperature range
0～70
0～100
0～70
0～200
0～70
0～ 100
—20～70
—20～100
—25～200
—20～70
—20～100|| tt||—25～200
0～70
0～100
0～200
0～70
0～200
Thermocouple graduation number
4.6 Marking
Compensation wire model
The marking of the product should be in the following format:
For example:
GB/T 4989--94
Continued Table 3
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
General ordinary grade
Heat-resistant ordinary grade
General precision grade
Heat-resistant precision grade
Insulation layer materials
And sheath materials
Using temperature range
20~70
—20~100|| tt||—25~~200
20~70
—20~100
-25~200
—20~100||tt| |25~200
20~70bzxZ.net
—20~100
—25~200
20~70
—20~10 0
-25～200
20～70
-20～~100
25～200
—20～70||tt ||—20～100
—25～200
20～70
20~100
25～200
SC-HS 2X1.5F BR'P
口口口
GB/T 4989—94
GB4989-94
Year of Standard
Standard Number
With Shielding Layer (No Standard for No Shielding Layer)
Soft Wire Core (No Standard for Hard Wire)
Sheath Material (B, F, V100, V70)
Insulation Layer Material (FV100, V70)
Single Core Section
Number of Cores (Single or Multiple Pairs)
Tolerance Grade (No Standard for Ordinary Grade)
Heat Resistance Grade (G, H)
Model (RC, KC A, KCB, KX,
NC, NX, EX, JX, TX)
Note: V100, V70 means the temperature resistance grade of PVC material is 100℃, 70℃ 5 Technical requirements
5.1 Thermoelectric characteristics and tolerances
When the reference end temperature is 0℃, the relationship between the thermoelectric electromotive force and temperature of the compensation conductor shall conform to the S, K, N, E, J and T graduation tables in GB3772, GB2614, ZBN05004, GB4993, GB4994 and GB2903 respectively, and the tolerance shall conform to the provisions of Table 4. Table 4
SC or RC
SC or RC
Wire temperature range
0～100
—20～100
25～200
0～~100
0～200
—20～100
—25～200
—20～100
Use category
Precision grade
Tolerance, μV
±30(±2.5℃)
±60(±1.5℃)
±60(±1.5℃)
±60(±1.5℃)| |tt||±60(±1.5℃)
±60(±1.5℃)
±60(±1.5℃)
±60(±1.5℃)
±60(±1.5 )
±60(±1.5)
±120(±1.5℃)
General grade
±60(±5.0℃)
±60(±5.0℃)
±100(± 2.5℃)
±100(±2.5℃)
±100(±2.5℃)
±100(±2.5℃)
±100(±2.5℃)
±100(±2. 5℃)
±100(±2. 5℃)
±100(±2.5℃)
±100(±2. 5℃)
±200(±2.5)
Thermocouple measuring end
Temperature, ℃
Wire temperature range
-25~～200
-20～100
—25~200
20～100
-25~～200
GB/T 4989—94
Continued Table 4
Use classification
Precision grade
Tolerance, μ
±120(±1. 5℃)
±85(±1. 5 C)
±85(±1. 5 C)
±30(±0.5℃)
±48(±0.8℃)
Ordinary grade
±:200(±2.5℃)
±140(±2.5℃)
±140(±2.5℃)
±60(±1.0℃)
±90(±1.5℃)
Thermocouple measuring end
Temperature, C
Note: The tolerances listed in this table are expressed in microvolts. The tolerances expressed in degrees Celsius are related to the temperature of the thermocouple measuring end. The temperature values in brackets are converted according to the thermocouple measuring end temperature listed in the table.
5.2 Insulation layer and sheath coloring
5.2.1 The insulation layer and sheath coloring of the compensation conductor shall comply with the provisions of Table 5. Table 5
Insulation coloring
Compensation conductor model
SC or RC
Ordinary grade
General use
Sheath coloring
Heat-resistant use
Precision grade
Ordinary grade
According to user requirements, products colored according to the recommended coloring of IEC584-3 are allowed. See Appendix A (supplement). 5.3 Insulation layer, sheath and shielding layer
5.3.1 The core insulation thickness, sheath thickness and maximum outer diameter of the compensation conductor shall comply with the requirements of Table 6. Table 6
Classification for use
General use
Nominal cross section of core
Nominal thickness of insulation layer
Nominal thickness of sheath
Precision grade
Maximum outer diameter of compensating conductor, mm
Single strand core
Multi-strand soft core
Classification for use
Heat-resistant use
Nominal cross section of core
GB/T 4989--94
Continued Table 6
Nominal thickness of insulation layer
Nominal thickness of sheath
Maximum outer diameter of compensating conductor, mm
Single strand core
Note: ① For general compensating conductor, the thickness of the insulation layer is allowed to have a positive deviation, but the maximum outer diameter of the conductor shall not exceed the provisions of this table. ② If a shielding layer is added, the increase in the maximum outer diameter of the wire shall not exceed 1.6mm. 5.3.2 Insulation layer
5.3.2.1 The surface of the insulation layer of the general compensation wire shall be flat, uniform in color, and free of mechanical damage. Multi-strand soft wire core
3. 4×6. 2
5.3.2.2 The tolerance deviation of the insulation layer thickness of the general compensation wire is minus 10% of the nominal thickness, and the thickness at the thinnest point shall not be less than 90% of the nominal value minus 0.1 mm.
5.3.2.3 The insulation layer of the general compensation wire shall withstand the spark test of AC 50Hz and voltage 4000V without breakdown. The running speed of the test machine shall ensure that the insulation layer is subjected to voltage action for no less than 0.1s at each point. 5.3.2.4 The thickness of the insulation layer of the heat-resistant compensation conductor is allowed to deviate by no more than minus 20% of the nominal thickness, and the thickness at the thinnest part shall not be less than 90% of the nominal value minus 0.1mm. The outer diameter of the insulating core is allowed to be partially enlarged, but the outer diameter at the thick part shall not exceed the maximum outer diameter value. 5.3.3 Sheath
5.3.3.1 Where polyvinyl chloride or polytetrafluoroethylene is used as a sheath, the sheath shall be tightly wrapped on the insulation layer of the core, and there shall be no adhesion between the insulation layer and the sheath. The surface shall be flat and the color shall be uniform. 5.3.3.2 The thickness of the sheath is allowed to deviate by no more than minus 20% of the nominal value, and the thinnest part shall not be less than 80% of the nominal thickness. 5.3.3.3 The braiding density of the sheath woven with glass fiber shall not be less than 90%. 5.3.4 Shielding layer
5.3.4.1 The braiding density shall not be less than 80%, and the broken ends shall be trimmed neatly after connection. 5.3.4.2 The composite aluminum (copper) tape shall be tightly attached to the insulation layer and not easy to loosen. 5.3.4.3 The thickness of the shielding layer shall not be greater than 0.8mm. 5.4 Sheath marking
The surface of the sheath of the general compensation conductor shall be continuously printed with the manufacturer's name or trademark, conductor code, specification, operating temperature range and other marks. The markings are required to be clear and firm, and the distance between the marks shall not exceed 500mm. 5.5 Insulation resistance
When the ambient air temperature is 15-35℃ and the relative humidity does not exceed 80%, the insulation resistance between the cores of the finished compensation conductor and between the core and the shielding layer shall not be less than 5Ma per 10m.
5.6 Physical and mechanical properties
The physical and mechanical properties and aging properties of the insulation layer and sheath of the general compensation conductor shall comply with the provisions of Table 7. Table 7
Use classification
General use-20～70℃
—20～100℃
Physical and mechanical properties
Tensile strength, N/mm2
Elongation, %
≥125
≥125
Temperature, ℃
135±2
Aging properties
Time, h
Strength change rate, %
5.7 Heat resistance
GB/T 4989—94
After the heat-resistant compensating wire is subjected to a heat-resistant performance test at 220±5℃ for 24h, the sample is immediately bent 180° on a cylinder with a diameter five times its diameter, and the following requirements shall be met: a. No cracks on the surface;
b. The insulation resistance value per meter between the wire cores and between the wire core and the shielding layer shall not be less than 25Ma. 5.8 Moisture-proof performance
After the heat-resistant compensating wire is subjected to an ambient temperature of 40±2℃ and a relative humidity of 95±3% for 24h, the insulation resistance value per meter between the wire cores and between the wire core and the shielding layer shall not be less than 25MQ. 5.9 Low-temperature winding performance
General compensating wires shall be subjected to a low-temperature winding test at -20℃, and the insulation layer of the sample wound on the test rod shall be visually observed to be free of any cracks.
6 Test method·
6.1 Thermoelectric characteristic test
6.1.1 Test method
Measurement shall be carried out by comparison method.
6.1.2 Test instruments and equipment
a. Constant temperature oil tank: the temperature difference between any two points in its effective working range is less than 0.04℃; b. Electrical measuring instrument: low potential DC potentiometer with accuracy not less than 0.01 level and its corresponding supporting devices or other electrical measuring instruments and devices with the same level of accuracy,
c. Standard instrument: second-class standard mercury thermometer. 6.1.3 Sample preparation
Sampling shall be carried out in accordance with the provisions of Articles 7.2 and 7.3 of this standard, and the sample length shall be about 1~1.5m. First, strip off the insulation layer and sheath of about 10~~20mm long at both ends of the sample, and weld the two poles at one end into a spherical measuring end. The surface layer is smooth and scratch-free, and the diameter of the spherical end is about 2~3 times the wire diameter. The two poles at the other end are separated and connected to the measuring wire (copper wire) to form the reference end. 6.1.4 Test procedure
6.1.4.1 Test preparation
Insert the prepared measuring end of the sample into the constant temperature bath, and the insertion depth is not less than 200mm. Insert the reference end into the ice point thermostat (or ice bottle), and the insertion depth is generally about 150~200mm. Connect the measuring wire to the electrical measuring instrument, and then increase the temperature for measurement. 6.1.4.2 Measuring temperature point
When the reference end temperature is 0℃, the measuring end temperature is generally 100℃ using the compensation wire, and the heat-resistant compensation wire is 100℃ and 200℃. When reading, the temperature is controlled within ±1℃C, and the temperature fluctuation shall not exceed 0.05℃. During the type test, the thermoelectric emf value of the head and tail should be measured. After both ends are qualified, the maximum thermoelectric emf deviation value is taken. 6.2 Coloring
The coloring of the insulation layer and sheath of the compensation conductor shall be observed visually. 6.3 Structural dimension measurement
The outer diameter measurement, insulation layer thickness measurement and sheath thickness measurement of the compensation conductor shall be carried out in accordance with the provisions of GB2951.2, GB2951.3 and GB2951.4.
6.4 Marking test
The marking test is carried out by gently rubbing the sheath of the compensation conductor printed with the mark ten times with a piece of cotton or cotton cloth soaked in water. The mark can still be clearly identified.
6.5 Insulation resistance test
The insulation resistance test of the compensation conductor is carried out in the test environment specified in Article 5.5 of this standard, and the insulation resistance value is measured with a 500V9
megohmmeter with an accuracy of 1.0.
6.6 Physical and mechanical properties test
GB/T 4989-94
The physical and mechanical properties test of the insulation layer and sheath of the compensation conductor shall be carried out in accordance with the provisions of GB2951.6 and GB2951.7. 6.7 Heat resistance test
Take a test sample of not less than 1m from the finished product and place it in a thermostat at a temperature of 220±5℃ (200℃ level) (the sample should not touch the wall of the device). After 24 hours, take it out and immediately place the sample on a cylinder five times lighter than its straightness and bend it 180°. Observe with your eyes whether there are cracks. If there are no cracks, conduct an insulation resistance test in accordance with the method in Article 6.5 of this standard. 6.8 Moisture resistance test
Take a test sample of 1.5m long from the finished product and place it in a thermostat at 40±2℃, and keep the relative humidity at 95±3%. After 24 hours, measure the insulation resistance between the wire cores and between the wire core and the shielding layer according to the method specified in Article 6.5 of this standard. 6.9 Low temperature winding test
The low temperature winding test shall be carried out in accordance with the provisions of GB2951.12. 7 Inspection rules
7.1 Inspection classification
Product inspection is divided into factory inspection and type inspection. 7.2 Factory inspection
7.2.1 Factory inspection shall be carried out according to the counting sampling procedure of GB2828, and a single sampling plan shall be adopted. Among them, Class C defects shall be inspected by the whole roll, and Class B defects shall be inspected by taking about 1.5m at any end of the sample roll. 7.2.2 The inspection items, classification, inspection sequence, inspection level (IL) and qualified quality level (AQL) of factory inspection are shown in Table 8, and the sample size (n) and judgment array (A, R.) are shown in Table 9. Table 8
Unqualified categories
16~25
91~150
Note: N represents batch (volume).
7.3 Type inspection
Inspection items
Insulation layer and sheath coloring
Structural dimensions (maximum outer diameter for inspection)
Sheath marking
Insulation resistance
Thermoelectric characteristics and tolerances
7.3.1 Type inspection shall generally be carried out in the following cases:10
GB/T 4989--94
Trial production and identification of new products or old products transferred to the factory for production; After formal production, if there are major changes in structure, materials, and processes; During normal production, inspection shall be carried out at least once a year; When the product is resumed after long-term suspension; When there is a major difference between the factory inspection results and the last type inspection; When the national quality supervision agency proposes the requirement for type inspection. 7.3.2 Type inspection shall be carried out according to the counting sampling procedure of GB2829, and the sub-sampling plan shall be adopted. In the sample extraction, each coil head is 10~12m, and the tail is about 1.5m for testing.
7.3.3 The grouping, inspection sequence, discrimination level (DL), unqualified quality level (RQL), judgment array (Ac, R), and sample size (n) of type inspection items are shown in Table 10.
Unqualified category
8 Packaging and marking
8.1 Packaging
Inspection items
Insulation layer and sheath coloring
Structural dimensions
Sheath marking
Moisture resistance
Low temperature winding performance
Thermoelectric characteristics and tolerance
Insulation resistance
Physical and mechanical properties and aging performance
Heat resistance
8.1.1 The finished compensation conductor should be supplied in rolls (or drums), and each roll (drum) can only consist of one head. Each roll should be bundled at least 3 places and wrapped with moisture-proof material. When wound on the reel, the wires should be arranged neatly, the wire ends should be fixed, and they should be packed with moisture-proof material. 8.1.2 The delivery length is 200m or an integer multiple of 100m. It can also be delivered in any length according to the agreement between the two parties. The error in length measurement should not be greater than 0.5%. Short segments not shorter than 20m are allowed to be delivered, but the quantity should not exceed 10% of the total length of delivery. 8.2 Marking
Each roll (reel) of compensating wire should be marked after wrapping: 8.2.14
Manufacturer name and trademark;
Product name;
Product mark;
Product number,
Length and gross weight of each roll;
Year, month and day of manufacture. The product certificate of the compensating wire should indicate: manufacturer name and trademark;
Product name;
Product mark;
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