An industrial thermocouple is a component composed of one or more pairs of hot electrodes and insulators. It is used to prevent short circuits between the hot electrodes and/or between the hot electrodes and the protection tube, and protect the hot electrode components from environmental damage. If the affected tube is correctly connected to the thermocouple used, move the reference end of the thermocouple to the output end of the pair of wires. When there is a step change in temperature, the time required for the output of the thermocouple to change to a certain percentage of the step change, usually expressed as τ.

Industry Standard

The People’s Republic of China Professional Standard UDC Specification for industrial thermocouple assemblies ZB N11 002-87 Specification for industrial thermocouple assemblies instead of ZBY 026-81 Disassembled industrial thermocouple. For other forms of industrial thermocouples, part or all of the clauses in this standard can be used as reference.

International practical temperature scale.

The Celsius temperature scale (℃) stipulates: Under standard atmospheric pressure, the melting point of ice is 0 degrees, the boiling point of water is 100 degrees, and the middle is divided into 100 equal parts, each divided into 1 degree Celsius, and the symbol is °C.

The Fahrenheit temperature scale (℉) stipulates: Under standard atmospheric pressure, the melting point of ice is 32 degrees, the boiling point of water is 212 degrees, and the middle is divided into 180 equal parts, and each equal part is 1 degree Fahrenheit. The symbol is ℉.

The thermodynamic temperature scale (symbol T) is also called the Kelvin temperature scale (symbol K), or absolute temperature scale, which stipulates that the temperature at which the molecular motion stops is absolute zero.

The international practical temperature scale is an international agreement temperature scale, which is similar to the thermodynamic temperature scale, and has high reproducibility and is easy to use. The internationally used temperature scale is the '1968 International Practical Temperature Scale-1975 Revised Edition' adopted by the 15th International Conference on Power in 1975, which is recorded as: IPTS-68 (REV-75). However, due to the unpredictable temperature of IPTS-68, the International Committee of Weights and Measures authorized the 1989 meeting to pass the 1990 International ITS-90, ITS-90 temperature scale to replace IPS-68 in the seventh resolution of the 18th International Conference on Metrology. my country has fully implemented the ITS-90 international temperature standard since January 1, 1994.
Industrial thermocouple

The terms and definitions specified by ZBY 300 and the following terms and definitions apply to this standard.

1.1 Detachable industrial thermocoule assembly (industrial thermocoule assembly) The thermal electrode assembly can be taken out from the protective tube industrial thermocouple (hereinafter referred to as 'thermocouple').
Industrial thermocouple
Industrial thermocouple
1.1.1 Thermocoule element (thermocoule element) A component composed of one or more pairs of thermoelectrodes and insulators.

1.1.2 Insulation material is a part or material used to prevent short circuits between hot electrodes and (or) between hot electrodes and protective tubes.

1.1.3 Protective tube A tube used to protect the thermoelectrode assembly from harmful effects of the environment.

1.2 Compensating wires (extension or compensating cables) A ??pair of wires used with thermocouples. If it is correctly connected to the thermocouple used, move the reference end of the thermocouple to the output end of the pair of wires.

1.3 Test temperature points (temperature points for verification) The test temperature selected in order to check whether the thermocouple meets the tolerance requirements.

1.4 Limiting temperature (limiting temperature) The maximum applicable temperature and the minimum applicable temperature of the thermocouple. The highest applicable temperature is called the upper limit temperature, and the lowest applicable temperature is called the lower limit temperature.

1.5 Insulation resistance (insulation resistance) For a thermocouple with a pair of hot electrodes, it refers to the resistance between the hot electrode and the protection tube; for a thermocouple with multiple pairs of hot electrodes, it also refers to the resistance between the pairs of hot electrodes .

1.6 Thermal response time (thermal response time) When there is a step change in temperature, the time required for the output of the thermocouple to change to a certain percentage of the step change, usually expressed as τ.

skills requirement
2.1 Assembly quality and appearance The assembly quality and appearance of the thermocouple should meet the following requirements: a. The welding of the measuring end of the hot electrode should be smooth, firm, free of defects such as pores and dust, and no residual flux and other dirt; b. The assembly is correct, the connection is reliable, and the parts are not damaged or missing; c. There is no open circuit or short circuit; d. There is no residual dirt and metal scraps in the protection tube; e. Correctly mark the polarity at the appropriate position; f. The surface coating is uniform and firm ; The National Machinery Industry Commission approved the implementation of 1998-01-01 g. No significant rust, dents, or scratches.

2.2 Tolerance The tolerance of thermocouple should comply with ZBY 300 regulations. Note: ① For S-type and T-type thermocouples with tolerance class I, the temperature of the thermoelectrode reference junction is 0℃. ② For thermocouples with non-detachable compensation wires, the thermoelectrode-compensation wire assembly should meet the requirements of this article.

2.3 Insulation resistance

2.3.1 The normal temperature insulation resistance of the normal temperature insulation resistance thermocouple should meet the following requirements: a. For a thermocouple with a length of more than 1m, the product of its normal temperature insulation resistance value and its length should not be less than 100MΩ·m, that is, Rr·L≥100MΩ· m L>1m (1) Where: Rr-the insulation resistance value of the thermocouple at room temperature, MΩ; L-the length of the thermocouple, m. b. For a thermocouple with a length of less than 1m, its normal temperature insulation resistance value should not be less than 100MΩ.

2.3.2 Upper-limit temperature insulation resistance The upper-limit temperature insulation resistance value of the thermocouple should not be less than that specified in Table 1.

Table 1 Upper limit temperature tm, ℃ Test temperature t, ℃ Resistance value, MΩ 100≤tm<300 300≤tm<500 500≤tm<850 850≤tm<1000 1000≤tm<1300 tm≥1300 t = tm t = tm t = tm t = tm t = tm t = 1300 10 2 0.5 0.08 0.02 0.02

2.4 Thermoelectric thermal stability thermocouples (except T, E, K types with tolerance level III) should be kept at the upper limit temperature specified by the manufacturer for 250 hours, and the change in thermoelectromotive force at the highest inspection temperature before and after the test (converted The change in temperature) should not exceed the requirements in Table 2.

Table 2 Code of tolerance grade thermocouple Ⅰ Ⅱ Ⅲ S 1℃ or [1+(tmax-1100)×0.003] ℃ 1.5℃ or 0.25% tmax-B-1.5℃ or 0.25% tmax 4℃ or 0.5% tmax T 0.5 °C or 0.4% tmax 1 °C or 0.75% tmax-JEK 1.5 °C or 0.4% tmax 2.5 °C or 0.75% tmax-Note: tmax-the highest inspection temperature point, °C shall be selected from the two allowable values ??given in the same column Larger value.

2.5 Transport basic environmental conditions Thermocouples should be able to withstand the continuous impact and free drop tests specified in ZBY 002-81 'Basic Environmental Conditions and Test Methods for Transportation, Transportation and Storage of Instruments and Meters'.

2.6 Thermal response time The thermal response time of the thermocouple should conform to the value provided by the manufacturer in the instruction manual.

experiment method
3.1 Assembly quality and appearance The inspection of assembly quality and appearance shall be performed visually and with appropriate instruments and equipment.

3.2 Tolerance

3.2.1 Inspection temperature points The inspection temperature points should be selected in accordance with Table 3, and other suitable inspection temperature points can be supplemented when necessary. Table 3 Thermocouple Type Code Tolerance Level Inspection Temperature Point Platinum Rhodium 10%-Platinum S Ⅰ 419.58℃, 630.755℃, 1084.88℃ Ⅱ 630.755℃, 1084.88℃ Platinum Rhodium 30%-Platinum Rhodium 6% B Ⅱ 630.755℃, 1084.88℃ , 120℃, 1400℃, 1600℃ Ⅲ 630.755℃, 1200℃ Iron-copper-nickel (constantan) J Ⅰ, Ⅱ within the applicable temperature range every two hundred degrees Celsius (including upper limit temperature) Copper-copper-nickel (constantan) T Ⅰ, Ⅱ Every 100 degrees Celsius (including upper limit temperature) within the applicable temperature range Ⅲ -195.806°C, -78.476°C Ni-Cr-Cu-Ni (Constantan) Ni-Cr-Ni-Si EK Ⅰ Every 200 degrees Celsius within the applicable temperature range (Including the upper limit temperature) Ⅱ Every 300 degrees Celsius (including the upper limit temperature) within the applicable temperature range Ⅲ -195.806°C, -78.476°C Note: ① The allowable deviation range of the actual inspection temperature value is ±10°C; ② The inspection temperature should be in thermoelectric Even within the applicable temperature range.

3.2.2 Inspection equipment

3.2.2.1 Standard thermometer The uncertainty of the standard thermometer should not exceed one third of the allowable error of the thermocouple being tested. The following standard thermometers are recommended: a. Standard platinum resistance thermometer, operating temperature range -196~630.74℃; b. Standard platinum rhodium 10-platinum thermocouple, operating temperature range 300~1200℃; c. Standard platinum rhodium 30-platinum Rhodium 6 thermocouple, operating temperature range 1200~1600℃;

3.2.2.2 The thermostats used in the tolerance test by the comparison method are: a. Precision thermostats: the temperature difference between any two points of each intubation within a working area of ??100mm along the intubation direction does not exceed 0.1℃; b. Tubular furnace: the length of the furnace is not less than 600mm, and the temperature difference in the working area not less than 60mm near the furnace center is not more than 1℃; the tube furnace is only used with standard thermocouples. The temperature of the precision constant temperature device should not change more than 0.1°C within a specified time; the temperature of the tube furnace should not change more than 1°C within a specified time; the specified time should be the largest of the following three times: Thermal response time of standard thermometers 5 times of τ0.5. The thermal response time τ0.5 of the tested thermoelectrode assembly (or thermocouple) is 5 times. The time required to test at a test temperature point.

3.2.2.3 0°C Thermostat The length of the 0°C thermostat intubation should not be shorter than 160mm, and the temperature of the working area is -0.1~+0.1°C. 3.2.3 Inspection methods and requirements The tolerance inspection is generally performed on the thermoelectrode assembly. In the inspection, the comparison method is generally used, and the fixed-point method can also be used for the inspection at temperature points such as -195.806℃, -78.476℃, 100℃, 419.58℃, 630.755℃, 1084.88℃. The requirements for temperature compensation of electrical measuring instruments and reference junctions are shown in Table 4.

Table 4 Tolerance level Ⅰ Ⅱ Ⅲ S Electrical measuring instrument category AB-Reference junction temperature compensation adopts 0℃ thermostat or other reference junction temperature compensation methods-B Electrical measuring instrument category-AB reference junction temperature Compensation-The ambient temperature is within the range of 0-40℃ without compensation. J Electric measuring instrument category AB-Reference junction temperature compensation adopts 0℃ thermostat, 0℃ thermostat or other reference junction temperature compensation methods-T Electric measuring instrument category AB reference junction temperature compensation adopts 0℃ thermostat E, K electrical measuring instrument category AB reference junction temperature compensation adopts 0℃ thermostat adopt 0℃ thermostat or other reference junction temperature compensation methods Note: ① Class A electrical measuring instrument The accuracy level is not less than 0.01, and the resolution is not less than 0.1μV; the accuracy level of the B-type electrical measuring instrument is not less than 0.05, and the resolution is not less than 1μV; ② If other reference junction temperature compensation methods are used , The compensation error should not be more than one third of the allowable temperature tolerance of the tested thermocouple at the reference junction.

3.3 Insulation resistance

3.3.1 Inspection requirements a. The thermocouple shall be subjected to insulation resistance test according to the original assembly method at the factory. b. The accuracy of the instrument used to measure the insulation resistance is not less than ±20%. c. The test voltage is applied for 60 seconds, and the insulation resistance value is recorded. d. The direction of the applied test voltage should be changed, and the measurement results should be recorded separately, and the smaller value should be the insulation resistance value of the thermocouple under test.

3.3.2 Normal temperature insulation resistance The test voltage of normal temperature insulation resistance is DC 500±50V. The atmospheric conditions for measuring the insulation resistance at room temperature are: temperature 15~35℃, relative humidity 45%, atmospheric pressure 86~106kPa. The thermocouple under test should be placed in such atmospheric conditions for at least 2 hours before testing.

3.3.3 Upper-limit temperature insulation resistance The test voltage of the upper-limit temperature insulation resistance is DC 10±1V. The time the thermocouple under test stays at the test temperature should not be less than 5 times its thermal response time τ0..5. The deviation range of the test temperature from the upper limit temperature is ±10℃. The heated length of the thermocouple is 300mm or 50% of the total length (choose the smaller value and allow a deviation of 10%). The temperature unevenness of the heating zone should be within 10°C. For the thermocouple using the ceramic protection tube, use a metal wire to evenly wind 15 to 20 turns on the heated part of the thermocouple ceramic protection tube as one pole of the upper temperature insulation resistance test. The metal wire used should be harmless to the thermocouple.

3.4 Thermoelectric thermal stability

3.4.1 Inspection requirements The thermoelectromotive force stability test of the thermocouple shall be carried out with a protective tube. For thermocouples with a sealed junction box, the junction box should be properly sealed during the test.

3.4.2 Inspection method a. Measure the thermoelectromotive force of the tested thermocouple near the highest inspection temperature point according to the method specified in Article 3.2, and convert the measurement result into the thermoelectromotive force value corresponding to the highest inspection temperature point [for conversion method see Appendix B .1 (reference piece)]. b. Put the tested thermocouple in the test furnace, then raise the test furnace to the temperature specified in 3.4.1 and maintain it for 250 hours. c. Repeat step a after natural cooling. d. Calculate the thermoelectric heat change according to formula (2) △E △E = Ec-Ea ----------------------------- ------------ (2) Where: Ec, Ea - are the results measured in step c and step a, respectively.

3.5 Basic environmental conditions for transportation Carry out continuous impact and free drop tests in accordance with ZBY 002. For general thermocouples, the free fall height is 250mm; for fragile and vulnerable thermocouples, the free fall height is 50mm.

3.6 Thermal response time

3.6.1 The inspection requirements shall record the time τ0..9 when the output of the thermocouple changes to 50% of the temperature step change. If necessary, the thermal response time τ0..1 with a change of 10% and the thermal response time with a change of 90% can be additionally recorded. Response time τ0..9. The recorded thermal response time should be the average of at least three test results of the same test, and the deviation of each test result from the average should be within ±10%. The time required to form a temperature step change should not exceed one-tenth of the τ0.5 of the thermocouple under test. The response time of the recording instrument or meter should not exceed one-tenth of the τ0.5 of the thermocouple under test.

3.6.2 Inspection method In the available cross-section of the test flow channel, the water flow rate should be maintained at 0.4±0.05m/s, and the initial temperature should be within the range of 5~45℃. The temperature step value is 40~50℃. During the test, the temperature change of the water should not exceed ±1% of the temperature step value. The insertion depth of the tested thermocouple is 150mm or the designed insertion depth (choose the smaller value and indicate it in the test report). The thermal response time of type B thermocouple is recommended to be tested by the following method: replace its own thermoelectrode assembly with the thermoelectrode assembly of type S thermocouple of the same specification, and then perform the test. Note: Other test methods can be used by the manufacturer and the user, but the data given must indicate the test conditions.


testing regulations


4.1 General Rules Each thermocouple must pass the factory test before leaving the factory; thermocouple products of various structures and temperature ranges should be sampled for type tests on a regular basis. All thermocouples with special structures and intended to be used in harsh environments should undergo additional type tests [see Appendix A (Supplementary)]. The items and cycles of additional type tests shall be negotiated by the manufacturer and the user.

4.2 Sampling rules are carried out in accordance with GB 2829-81 'Periodic Inspection Attribute Sampling Procedure and Sampling Table', and stipulate: a. The inspection period shall not exceed two years; b. The discrimination level is recommended to be level 1; c. The unqualified quality level shall not exceed 5; d. Take a sampling plan once and determine the array as AC=0 and Re=1.

4.3 Factory test

4.3.1 Items and sequence a. Tolerance; b. Assembly quality and appearance; c. Normal temperature insulation resistance.

4.3.2 Test temperature point a. For thermocouples of S type, J type, T type, E type, and K type with tolerance levels of Ⅰ and Ⅱ, they should be allowed at an inspection temperature point not lower than 100℃. Tolerance inspection; b. For T-type, E-type, and K-type thermocouples with tolerance level of Ⅲ, tolerance inspection should be carried out at an inspection temperature point lower than -100℃; c. For tolerance level of Ⅱ, Class Ⅲ type B thermocouples should be tested for tolerance at a test temperature not lower than 600℃.

4.4 Type test

4.4.1 Project a. Basic environmental conditions for transportation; b. Assembly quality and appearance; c. Normal temperature insulation resistance; d. Thermal response time; e. Upper temperature insulation resistance; f. Tolerance; g. Thermal electromotive force stability.

4.4.2 Sequence Determine the type test sequence according to the following priority: a. Test without changing the original packaging method; b. First short-term and then long-term; c. Test without changing the original assembly method; d. First low temperature and then high temperature ( Excluding the order of each inspection temperature point during tolerance inspection).

4.5 Discrimination rules for tolerance inspection When using the manufacturer's measurement system for tolerance inspection, if the manufacturer's measurement system has an error of ±n°C, the test result should not exceed ±(△-n)°C (△ is 2.2 The specified tolerance value); when using the measurement system of the acceptance unit for tolerance inspection, if the error of the measurement system of the acceptance unit is ±m℃, the test result should not exceed ±(△+m)℃.


Information that packaging and thermocouple manufacturers should provide to users

5.1 Packaging a. Thermocouples generally adopt simple packaging as specified in ZBY 003-85 'Technical Conditions for Packaging of Instruments and Meters'. b. Thermocouples with porcelain protective tubes and other fragile and vulnerable thermocouples should be in shock-proof packaging specified by ZBY 003.

5.2 Information that should be indicated on the nameplate or the factory qualification certificate a. Model; b. Specifications; c. Code (graduation number); d. Applicable temperature range; e. Tolerance level; f. Protection tube material; g. Trademark or manufacturer name; h. Date of manufacture.

5.3 Information to be provided in the instruction manual a. Index table; b. Thermal response time; c. Applicable environment; d. General use method; e. Special technical conditions.

Appendix A Additional Type Test (Supplement)

A.1 Technical requirements

A.1.1 Insulation resistance under damp and heat conditions At the end of the constant damp and heat test of thermocouples, the insulation resistance value should not be less than 10MΩ.

A.1.2 Unpackaged free fall The thermocouple shall have no mechanical damage, no open circuit or short circuit at the end of the unpackaged free fall test, and the normal temperature insulation resistance shall meet the requirements of paragraph 2.3.1.

A.1.3 Vibration At the end of the vibration test, the thermocouple should have no mechanical damage, no open circuit or short circuit, and the insulation resistance at room temperature should meet the requirements of paragraph 2.3.1.

A.1.4 Pressure When the thermocouple is subjected to the test pressure, there should be no leakage, no mechanical damage, no open circuit or short circuit, and the insulation resistance at room temperature should meet the requirements of paragraph 2.3.1.

A.1.5 Protection against liquid intrusion The thermocouple shall have no mechanical damage, open circuit or short circuit at the end of the liquid intrusion protection test, and no visible water mark in the junction box. The insulation resistance at room temperature shall comply with the requirements of paragraph 2.3.1. .

A.1.6 Explosion-proof thermocouples shall be tested by an agency designated by the state, and the agency shall issue a certificate in accordance with national regulations.

A.2 Test method

A.2.1 Insulation resistance under damp and hot conditions Test according to GB2423.3-81 'Basic Environmental Test Procedures for Electrical and Electronic Products Test Ca: Constant Damp Heat Test Method'. The duration of the test is 2 days. At the end of the test, immediately measure the insulation resistance value of the thermocouple under test at room temperature according to 3.3.

A.2.2 Free fall without packaging Before the free fall test, the thermocouple under test should be structurally complete. The test device is a steel plate with a thickness of 6mm laid on a rigid ground. During the test, the longitudinal axis of the tested thermocouple was basically parallel to the surface of the steel plate, and the distance between the two was about 250mm. Then let the tested thermocouple fall freely from this height onto the steel plate. This process should be repeated ten times. At the end of the test, immediately check the tested thermocouple for mechanical damage, open circuit or short circuit, and measure the normal temperature insulation resistance value according to 3.3.

A.2.3 Vibration Test according to GB4451-84 'Industrial Automation Instrumentation Vibration (Sine) Test Method'. The vibration level can be 2B or 2C according to the actual situation. At the end of the test, immediately check whether the tested thermocouple is mechanically damaged. Whether there is open circuit or short circuit, and measure the insulation resistance value at room temperature according to 3.3.

A.2.4 Pressure The thermocouple to be tested is placed in a pressure test tube filled with liquid, and the pressure is gradually increased to 1.5 times the maximum operating pressure and maintained for 60 seconds. At the end of the test, immediately check the tested thermocouple for leaks, mechanical damage, open circuit or short circuit, and measure the insulation resistance value at room temperature according to 3.3.

A.2.5 Protection against liquid intrusion can be selected from the three levels described in paragraph A.2.5.1, paragraph A.2.5.2, and paragraph A.2.5.3 (the severity of which is increasing) according to actual conditions. test. At the end of the test, immediately check whether the tested thermocouple is mechanically damaged, whether there is an open circuit or short circuit, and whether there is any visible water mark in the junction box, and measure the normal temperature insulation resistance value according to 3.3. A.2.5.1 The principle of the test device is shown in Figure A. This device should have a semi-circular water spray pipe that can be oscillated back and forth. The radius of the semicircle should be as small as possible and meet actual needs. The swing angle α of the spray pipe relative to the vertical direction is ±60°, and the half angle β of the fan-shaped spray surface is ±60°. The time required to sweep through the angle α is about 1 second. The test pressure is 0.1MPa. The longitudinal axis is basically perpendicular to the ground, and the junction box is roughly at the center of the semicircular water spray pipe. During the water spray test, the tested thermocouple rotates 180° around its axis every 300 seconds, and the water spray test time is at least 10 minutes. This picture is 'inverted picture'

A.2.5.2 The principle and test method of the test device are the same as in A.2.5.1. But α is about ±180°, β is about ±90°, and it takes about 0.5 seconds to sweep the α angle.

A.2.5.3 The test device is a water spray nozzle with an inner diameter of 12.5mm, the test pressure is 0.1MPa, and the distance from the water spray nozzle to the junction box of the tested thermocouple is 3m. During the test, the water spray nozzle should spray water to the thermocouple under test from all directions. The water spray test time is at least 15 minutes.

A.2.6 Explosion-proof test Carry out the test in accordance with the relevant regulations of GB3836-83 'Explosion-proof electrical equipment 'd''.

Appendix B Supplementary Explanation (Reference)

B.1 Conversion method If the actual test temperature has a small deviation from the test temperature point, the conversion surface of the thermoelectromotive force measurement result can be converted to the thermoelectromotive force value of the test temperature point according to the following method. E(t)=E(t')+(t-t')-------------------------- (3) where: t --Inspection temperature, ℃; t'­-- actual inspection temperature measured by a standard thermometer, ℃; E(t)--thermoelectric heat of thermocouple at temperature t, μV; E(t')- -The thermoelectric heat of the thermocouple when the temperature is t', μV; --The sensitivity or Seebeck coefficient of the thermocouple when the temperature is t, μV·℃-1. It can be calculated according to the formula given in the appendix of ZBY300, or it can be calculated from the following formula = -------------------------------- --(4) Where: E*(t)--The thermoelectromotive force given by the thermocouple index table at temperature t, μV; Example: The thermoelectromotive force measured by a K-type thermocouple is 41.400mV, check The temperature is 1000°C, and the actual inspection temperature measured with a standard thermometer is 1005.5°C. mV/ ℃ E(1000℃)= 41.400+0.0389×(1000-1005.5) = 41.186mV The thermoelectromotive force of this thermocouple is 41.186mV at 1000℃.

B.2 Other main standards related to this standard

B.2.1 Thermoelectrode a. GB3772-83 'Platinum rhodium 10-platinum thermocouple wire and indexing table'; b. GB2909-82 'Platinum rhodium 30-platinum rhodium 6 thermocouple wire and indexing table'; c. GB4994 -85 'Iron-copper-nickel thermocouple wire and indexing table'; d. GB2903-82 'Copper-Constantan thermocouple wire and indexing table'; e. GB4993-85 'Nickel chromium-copper-nickel thermocouple wire and Index table'; f. GB2614-85 'Nickel-chromium-nickel silicon thermocouple wire and index table';

B.2.2 Compensation Wire GB4989-85 'Compensation Wire for Thermocouple'.

B.2.3 Porcelain protection tube and insulating tube GB2935-82 'Porcelain sleeve for thermocouple'.

Common product classification:

Industrial thermocouple
Assemble thermocouple
Explosion-proof thermocouple
Armoured thermocouple
Micro armored thermocouple
Wear-resistant thermocouple
Multipoint thermocouple
Blowing thermocouple
Compression spring fixed thermocouple
Multi-point flameproof thermocouple
High temperature anticorrosive thermocouple
High temperature and high pressure thermocouple
Furnace tube blade thermocouple
Right angle elbow thermocouple
Special thermocouple for cracking furnace
Fast thermocouple/temperature gun
High temperature precious metal thermocouple
Wear-resistant cut off thermocouple
Wear-resistant leakage thermocouple