GB/T 2974-1982 Test methods for thermocouple wires for industrial use
Some standard content:
National Standard of the People's Republic of China
Testing methods for industriat thermocouple wiresUDC 536.516
: 620,1
GB2974—82
This standard applies to the basic requirements for the inspection of domestic industrial-graded characteristic U nickel-chromium-nickel-silicon, EA nickel-chromium-copper thermocouples and thermoelectrodes
1.1 The allowable deviation of the thermoelectric potential (when the cold end temperature is 0℃) for the indexing table shall be in accordance with the provisions of Table 1. Table 1
Name of the thermocouple
Nickel-chromium-nickel-silicon
Nickel-chromium-copper steel
Working end overflow
Note: "It is the working end temperature of the thermocouple.
Allowable deviation
Working end temperature
Allowable code-difference
1.2 The surface of the thermocouple and the wire to be tested should be uniform, straight and smooth, without oil stains, folding, corrosion, cracks, burrs, interlayers and fragility.
1.3 The hot joint should be welded firmly, with a smooth surface and no air support. Instruments and equipment
2,1 Receiver
2.1.1 Low-resistance and high-resistance DC potentiometers and matching galvanometers (accuracy required according to requirements): 2.1.2 Second-class standard batteries, conversion switches or other instruments with equivalent measuring accuracy. 2.1.3 Second-class (third-class) armored standard thermocouples and second-class standard mercury thermometers, 2.2 Equipment || tt || 2.2.1 Tubular electric furnace: The high-temperature working area of the middle furnace is determined according to the length of the thermocouple and the temperature required for actual production: The furnace should be equipped with nickel blocks or High temperature alloy block, so that the temperature field in the furnace is stable. 2.2.2 Oil and water constant temperature increase: The temperature field in the working area should be uniform, and the vertical temperature difference at any point 300mm apart is less than 0.2℃.
2.2.3 A set of welding equipment,
National Standards Bureau 1982-03-25 issued
[98212:0 implementation
3 Inspection method
3.1 Inspection point
GB 2974-82
3.1.1--General inspection points are as specified in Table 2, and can also be determined according to actual needs. Table 2
Name of thermoelectric probe
Nickel-chromium-silicon
Nickel-chromium-silicon system
3.1.2 Inspection of each point below 300℃, compare with the standard mercury thermometer in oil and water, the thermoelectric probe in the glass test tube should be immersed in the same depth as the standard mercury thermometer, and the mouth should be tightly covered with cotton. After the temperature is constant, start the measurement. 3.1.3300 ℃ and above, and compare with the standard thermocouple in the tubular electric furnace. 3.2 Test of uneven thermoelectric potential of thermocouple wire 3.2.1 Take sections from both ends of each coil of thermocouple wire and assemble them into thermocouple form. Measure its commercial pole thermoelectric potential at the corresponding temperature. The value is the uneven thermoelectric potential of the thermocouple material and meets the standard requirements of thermoelectric adjustment wire. 3.2.2 Operation method: Raise the furnace temperature to the required temperature +50, insert the welded thermocouple wire working end into the furnace (constant temperature zone, insert the cold end into the ice point, and read the value after stabilization. 3,3 Test of thermocouple unipolar thermoelectric potential bZxz.net
Pair the thermocouple wire with the standard platinum wire for measurement. Select the test temperature and test point according to the diameter of the wire (according to the standard requirements of the thermocouple wire). The platinum grade purity requires Ra/R. 1.392 or above. There should be no more than two contacts along the entire length. Use the bipolar method for inspection. Note: The same pole method can also be used for testing.
3.4 Bipolar method (comparison method)
The circuit is shown in the figure.
Standard full plastic
Luxury electric difference meter
Be grid!
3.4.! The thermocouple to be tested is bundled around the standard storage-platinum thermocouple so that the working end is on the same plane, and then inserted into the highest source of the furnace, and the furnace mouth is plugged with asbestos rope; the cold end is on the same plane and inserted into the freezing point tank. If the freezing point is not used, the temperature of each cold end must be kept stable. The cold end temperature is measured with a mercury thermometer and corrected according to the following formula: E
In the formula: E-thermocouple thermoelectric potential value:
1, a thermocouple working end temperature, is the actual temperature to-thermocouple cold end temperature: is 0C:
GB 2974-82
Produce a thermocouple cold end temperature. It is the actual temperature. 3.4.2 Thermocouple thermoelectric potential measurement can be carried out within the range of +10℃ of the temperature of each test point given on the standard thermoelectric code certificate. When reading, read the thermoelectric potential of each thermocouple in turn starting from the standard thermocouple, and then proceed in reverse order. Each reading shall be no less than 2 times: standard—→tested 1—tested 2—→tested 3—→tested 44
standard—tested 1 →-—tested 2: →tested 3 →-43,4.3 · Deviation calculation
3.4,3.1 According to formula (1), calculate the thermoelectric potential of the standard and the thermocouple when the cold end temperature is and the working end temperature is the actual temperature:
3.4.3.2 Calculate the working end temperature of the standard and the thermocouple under test according to the standard thermocouple. 3.4.3.3 Calculate the deviation of the thermocouple under test according to the working end temperature of the thermocouple under test: Ae=ee
The thermoelectric potential value of the thermocouple under test at the corresponding test temperature point (obtained by looking up the table): I: e——
The corresponding thermoelectric potential value (obtained from the table) when the upper end temperature of the tested thermocouple is the actual temperature, then the actual thermoelectric potential value of the tested thermocouple is Ede
Thermocouple Thermoelectric Potential Test Appendix D:
4 Result Processing
A certificate of conformity shall be issued to those that meet the requirements of Table 1 of this standard after inspection, and correction values shall be given if necessary. 4.1
4.2 Thermocouples that fail to meet the standard requirements but meet production needs after inspection shall be determined by the inspection and use departments 4,3 The inspection cycle of thermocouples in use can be determined according to the use conditions and time: 4,4 The single-pole thermoelectric potential can be determined by the same pole method, 4.5 Thermocouple inspection can also be determined by the differential method (see Appendix A for details). When using the differential method, the standard thermocouple shall be in accordance with the requirements of Appendix B 5 Inspection of thermocouple compensation wires
See Appendix C
G:B 2974 .-82
Appendix A
Differential method
(Supplement)
People, 1 Connect the standard thermocouple of the same number to the thermocouple to be tested, and directly measure the thermoelectric potential difference. As shown in the circuit diagram. Standard couple
Connect to potentiometer
Tested!
Tested!
A, 2 Insert the bundled thermocouple (the working ends of each thermocouple do not touch each other and are located on the same plane) into the hole of the nickel block (or heat-resistant gold block) in the furnace without contacting the nickel block (if the bottom of the nickel block hole is filled with insulating material, it can be directly connected to the bottom), and then connect the lines according to the diagram. The cold end temperature does not need to be corrected, as long as it is kept at the same temperature. When the furnace temperature is stabilized at the test point temperature ±10℃, the measurement can be carried out. First measure the thermoelectric potential value E of the standard thermocouple (this value is only used as a basis for determining whether the furnace temperature is within the test point temperature ± 10C). Then read the thermoelectric potential difference value 4e of the reverse series group in sequence, and each group of readings is no less than 2 times. That is:
+4eAc3--ee
E4e+-4ede,-de4--4es
A,3 Data processing
Thermoelectric potential value E of the thermocouple to be tested (when the positive or negative pole of the thermocouple to be tested is connected to the "positive" end of the potentiometer): E,t= Fr禁+4e:
Where: E.—Thermoelectric potential value at each test point recorded in the standard thermocouple certificate; e1—The average thermoelectric potential value of the readings when the standard thermocouple and the thermocouple to be tested are reversed at each test point. A.4 Example:
The average thermoelectric potential difference between the standard nickel-chromium-nickel-silicon thermocouple and the nickel-chromium-nickel-silicon thermocouple tested in the range of ±10°C around 1000°C is: 4cm=-0.04 millivolts. From the certificate of the standard nickel-chromium-nickel-silicon thermocouple, it is found that when the cold end temperature is 0 and the working end temperature is 100, the thermoelectric potential value is Eiao standard=41.39 millivolts.
The thermoelectric potential value of the nickel-chromium-nickel-silicon thermocouple tested (cold end is 0°C) is: Fmt#=Eron#+4e1Goz-41.39+（-0.04)=41.35 full volts. GB297482
Appendix B
Technical requirements for standard nickel-chromium-silicon thermocouples (filler)
B, 1 Standard nickel-chromium-silicon thermocouples should be annealed at 1000℃ for 10 hours. The thermoelectric potential should be measured once after 6 hours of annealing, and once again after 10 hours. The potential difference between the two times should not exceed 30 microvolts, otherwise annealing should be continued. B.2 Standard nickel-lead-nickel-silicon thermocouples are tested with second-class standard platinum-platinum thermocouples, and the difference between the two tests is not more than 40 microvolts. B, 3 The test cycle of standard thermocouples is generally 300 hours (calculated according to the use time). According to the use and specific conditions, supervisory tests can be carried out at any time. The test results are compared with the thermoelectric potential of the corresponding points in the inspection certificate. Those that are not more than 80 microvolts can continue to be used, otherwise they should be inspected.
B.4 The repeatability error of standard nickel-chromium-nickel-silicon thermocouples is ±3℃. B.5 The appearance inspection and inspection points are the same as those in Articles t.2, 1.3, and 3.1 of this standard. GB 2974-82
Appendix C
Inspection of thermocouple compensation wires
(Supplement)
C, 1 The characteristics of the compensation wires shall meet the requirements of Table C1. Table C1
TThermoelectric regulator name for thermoelectric potential coordination with working end temperature of 1000℃ and cold zone temperature of 0℃
Nickel-chromium-nickel
Nickel-chromium-copper
C,2The thermoelectric potential generated by the compensation wire and copper wire in the thermocouple should meet the requirements of Table C2. Table C2
Allowable deviation
TThermoelectric potential compensation wire with working end temperature of 1000℃ and cold end temperature of 0℃Name
0Nickel
0.6White pot
13—0.5Short copper
401.5Mn copper
1. 99 ~ 2.29
-0.61 ~0.67
-4.61~4.91
3. 95 ~ 4. 23
It, 3Compensation wires that meet the requirements in the table can be graded at other inspection points if required by the user unit. C.4 Before testing the compensation wire, the insulation at both ends should be cleaned for about 15 mm, and one end should be twisted or welded into a thermocouple, and then tested with reference to this standard,
GB 297482
Thanks to D
Example of thermocouple thermoelectric potential test
(Supplement)
At the temperature point of 1000℃, the nickel-chromium-nickel silicon thermocouple was tested, and the arithmetic mean of the thermoelectric potential readings was 10.50 mV. The arithmetic mean of the thermoelectric potential readings of the standard platinum thermocouple was 9.421 mV. The mercury thermometer indicated that the cold end temperature was 20℃. When the cold end temperature was 20℃ and the working end temperature was 00℃, the thermoelectric potential value of the tested nickel-chromium-nickel silicon thermocouple was calculated from the standard platinum thermocouple graduation table: E.5=E20.0=0.113 mV
According to the formula in the standard text 3, 4.1 (1), we get: Ei.standard=E.*standard+Ec.standard= 9.421 +0.113 = 9.534.mV From the nickel-chromium-nickel-silicon thermocouple graduation table, we get: E. load - E, 2a.6 = 0.80 mV
According to the standard text 3.4: 1 (1) formula: E.. blue = E..*# + E....1# = 40.50 + 0.80 = 41.30 mV E. and E, are the thermoelectric potentials of the standard and the tested thermocouples when the cold end temperature is 0℃ and the hot end temperature is the actual temperature.
From the standard platinum-platinum thermocouple graduation table, we get the thermoelectric potential value when the cold end temperature is 0℃ and the working end temperature is 1000℃: F = 9.569 mV.
From the certificate of the standard platinum-…-platinum thermocouple, when the cold end temperature is 0℃ and the working end temperature is 1000℃, the thermoelectric potential value E=9.580 mV. The correction value of the standard thermocouple at 1000℃ is K=EE=9.569·9.580=0.011 mV, so the corrected thermoelectric potential value is:
E*#+K=9.534+（*-0.011）=9.523 mV. From the platinum energy-platinum thermoelectric hedgehog graduation table, 9.523 mV is equivalent to 996℃, which is the standard push and the working end temperature of the tested thermocouple. From the graduation table of the tested chromium-silicon thermocouple, when the cold end temperature is (℃ and the working end temperature is 996℃, the corresponding The corresponding thermoelectric potential value is e=41.16 millivolts, and the working end temperature is 1000C, which means the corresponding thermoelectric potential value is e=4! .32 millivolts. According to the formula in Item (2) of 3.4.3.3 of the standard text, the deviation of the thermocouple is 4e=e-41.32-41.16-0.16. The actual thermoelectric potential of the tested thermocouple is: Fe=41.30+0.16=11.16 millivolts.
Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by the Ministry of Nonferrous Metals Processing Industry. From the date of implementation of this standard: the former Ministry of Metallurgical Industry Standard YB76-71 "Industrial Thermocouple Wire Inspection Method" is used as the standard.
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