GB/T 4067-1999 Determination of temperature characteristic parameters of resistance of metal materials
Some standard content:
GB/T 4067--1999
This standard refers to the three standards of ASTM B70--1990 (1995) "Standard Measurement Method for Change of Resistance of Metallic Materials for Electric Heating with Temperature", ASTM B84-1990 (1995) "Standard Measurement Method for Temperature Constant of Alloy Wire for Precision Resistors" and ASTM B114-1990 (1995) "Standard Measurement Method for Temperature Constant of Sheet Material for Shunts and Precision Resistors". In order to meet the different needs of various metal materials including resistors and electric heating alloys for the detection of resistance temperature characteristic parameters, GB/T4067--1983 is revised. The main technical indicators of this standard are basically the same as those of the ASTM standard. In terms of temperature control accuracy and specific requirements for thermocouples, adjustments and supplements have been made in accordance with national conditions, which are slightly different from the ASTM standard. This revision of this standard has been modified in the following aspects: "Reference Standards", "Definitions" and "Principles" have been added. 1. The scope of application has been expanded, and the technical content of precision resistance alloy sheets (strips) and electric heating alloys has been added. 1. Two characteristic parameters, "resistance temperature factor" and "peak temperature", have been added to the terminology. The content that belongs to the "operating procedures" that varies according to specific circumstances has been deleted. The control of important influencing factors such as stress is stricter than before. From the date of implementation of this standard, it will replace GB/T40671983 "Method for Determination of Resistance Temperature Characteristic Parameters of Metallic Materials". Appendix A of this standard is a prompt appendix.
This standard was proposed by the State Bureau of Metallurgical Industry. This standard is under the jurisdiction of the Metallurgical Information Standards Research Institute. The drafting unit of this standard: Metallurgical Research Institute of Shougang Corporation. The main drafters of this standard: Li Limin, Zhang Xiaoyi, Li Xin. This standard was first issued in December 1983.
1 Scope
National Standard of the People's Republic of China
Testing method for electrical resistance-temperature characteristic parameters of metallic materialsGB/T 4067--1999
Replaces GB/T4067--1983
This standard specifies the definition, principle, test device, sample preparation, test current, measurement procedure, measurement result calculation, test report, accuracy and deviation of the test method for electrical resistance-temperature characteristic parameters of metallic materials and other related conductive materials. This standard is applicable to the determination of the relationship between the resistance and temperature of any metal or alloy wire or sheet when the curve is approximately parabolic and the corresponding resistance temperature constant and peak temperature within a suitable temperature interval, and to the determination of the characteristic parameters such as the resistance temperature factor and the average resistance temperature coefficient of any metal, alloy or other conductive material within a suitable temperature interval. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard was published, the versions shown were valid. All standards are subject to revision. Parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T8170—1987 Rules for numerical revision
JG141—88 Verification procedures for industrial platinum 10 (platinum 13)-platinum thermocouples JJG229-87 Verification procedures for industrial nickel-chromium-nickel silicon and nickel-chromium-copper thermocouples JJG351-84 Verification procedures for industrial platinum-copper thermistors 3 Definitions and symbols
3.1 Resistance temperature factor
The ratio of the resistance value at a specified temperature t to the resistance value at a reference temperature t., expressed in C.: R
Where: Ce
Resistance temperature factor;
R.—Resistance value at temperature t℃, α;
Resistance value at reference temperature \t.℃, α. 3.2 Average resistance temperature coefficient
The average change value of the resistance temperature factor corresponding to a temperature change of 1°C at temperature t, tz is expressed as αt,: R,—R
ap2 = R(t - t)
Where: az
Average resistance temperature coefficient at temperature ti, t2, ℃-1; Resistance value at starting temperature t℃,;
R2——Resistance value at ending temperature t2℃, Q; (t2>t)R.
——Resistance value at reference temperature toC,.
Approved by the State Administration of Quality and Technical Supervision on November 1, 1999 (1)
Implemented on August 1, 2000
3.3 Resistance temperature constant
GB/T 4067—1999
When the resistance-temperature relationship is close to a parabola, the coefficients of the first-order and second-order terms in the relationship are expressed as α and β: R, - R[1 + α(t to) + β(t - to)]Where: R, resistance value at temperature tC, Q;
R. —reference temperature t. ℃, α; t—test measurement temperature, ℃;
to—reference temperature, ℃;
α—secondary resistance temperature constant, -,
β—secondary resistance temperature constant, ℃-2. 3.4 Peak value temperature
The temperature at which the resistance is at its maximum value within the test temperature range is expressed as tm (C). 4 Principle
(3)
4.1 This measurement method uses a resistance measuring instrument to detect the resistance of a conductive material as a function of temperature; the currently commonly used single (double) bridge method, compensation method ('potentiometer method), digital ohmmeter and other equivalent resistance measuring devices can be selected as resistance measuring instruments as long as they meet the requirements of this standard.
4.2 Since resistance is a sensitive parameter, the temperature change and temperature measurement devices for electric heating materials and wire and sheet precision resistance material samples are specified based on the characteristic parameter measurement requirements; the quality of temperature measurement and control is one of the key factors affecting the measurement results. 5 Test Equipment
The complete test equipment consists of one or more thermostatic baths or furnaces that can heat the sample to the specified temperature, a temperature measuring instrument and an applicable sample resistance measuring instrument.
5.1 Thermostatic Bath or Furnace
5.1.1 Thermostatic Bath for Testing Precision Resistance Alloy Wire5.1.1.1 The liquid bath for the applicable temperature of -65 to 15°C can be composed of toluene or its equivalent; the liquid bath for the use temperature of 15 to 250°C can be composed of low-viscosity, chemically neutral oil, and the ignition point of the oil is required to be at least 50°C higher than the use temperature. 5.1.1.2 The liquid in the liquid bath must be sufficient to ensure that after stirring, the temperature around the sample and the thermometer is uniform: the temperature difference should be within 0.5°C in the range of -65 to 100°C, and within 1°C in the range of 100 to 250°C. If the temperature range is less than 100°C, the temperature uniformity index should be more stringent in proportion. Note: It is recommended to use a bath with dissolving ability at room temperature so that the sample can be rinsed before being immersed in a temperature tank. 5.1.2 Constant temperature bath for testing precision resistance alloy sheets (strips). 5.1.2.1 The tank contains chemically neutral oil; there must be enough liquid in the liquid tank to ensure that after stirring, the temperature difference between the sample and the area around the thermometer is no more than 0.2°C at any temperature between 0 and 80°C. 5.1.3 Temperature distribution and manual temperature control in the constant temperature bath 5.1.3.1 In the automatic temperature control bath, at any temperature and any time during the test, the difference between the temperature of any point in the bath and the average temperature is required to be no more than 0.2°C; when the temperature is manually controlled, the temperature change rate is required to not exceed 0.2°C/min. 5.1.4 Electric furnace for testing high temperature resistance of materials such as electrothermal alloys 5.1.4.1 The temperature of the furnace used to heat the sample should be controllable within the range from room temperature to the required maximum temperature; the structure of the furnace should ensure uniform temperature distribution at each temperature point tested in the section where the sample and thermocouple are placed. To prevent the influence of radiation, the sample and thermocouple should be shielded.
1) 20℃ is usually used as the reference temperature, the same below, 2) as "the average rate of change of resistance corresponding to a temperature change of 1℃ within a specified temperature range." 96
GB/T 4067—1999
5.1.4.2 In order to test the temperature uniformity of the section in the furnace where the sample is placed, a sample with representative size and a thermocouple should be placed in the center of the furnace, and the furnace should be heated to the highest test temperature and kept at this temperature. After that, the sample and the thermocouple should be moved in the direction of the maximum temperature gradient. This distance should be equal to the maximum possible size of the sample. For typical materials, the difference between the two temperatures before and after is required to be no more than 1%.
5.1.4.3 The temperature controller used should be able to control the test temperature within ±5℃. 5.2 Temperature measuring instrument
5.2.1 Thermometer for detecting precision resistance alloy wire 5.2.1.1 The uncertainty of temperature measurement shall be ±0.5°C or 1% of the entire temperature range, whichever is smaller. 5.2.2 Thermometer for detecting precision resistance alloy strips (sheets) 5.2.2.1 The temperature shall be detected by a laboratory mercury thermometer or resistance thermometer. The thermometer sensitivity shall be able to indicate a temperature change of 0.1°C; within the range of 0 to 80°C, the measurement uncertainty of the temperature difference shall be 0.2°C. 5.2.3 Thermometer for detecting high temperature resistance of materials such as electric heating alloys 5.2.3.1 This system consists of a calibrated temperature sensor device or device group and a manual, electronic or other equivalent readout device. The temperature indication value to be detected is required to be better than ±0.5°C. 5.2.3.2 As this test method covers a wide temperature range, different types of sensors can be used depending on the temperature range. Generally, wire (32AWG or finer wire) or foil thermocouples calibrated according to the JJG141 or JJG351 verification procedures and wire resistance thermometers calibrated according to the JJG229 procedures are used.
5.2.3.3 In the range of 190~350℃, it is recommended to use E-type or T-type thermocouples, and in the range of 0~900℃, it is recommended to use K, S and N-type thermocouples. Thermocouples should be calibrated regularly to ensure that they are not contaminated during use or that phase changes caused by the migration of alloy components at the junctions affect the accuracy of temperature measurement. 5.2.3.4 When using thermocouples, an ice water tank or an equivalent electronic reference device that is not affected by changes in ambient temperature should be used to ensure that the reference end is 0℃.
5.2.3.5 The temperature should be detected by a calibrated thermocouple connected to a potentiometer; when an optical pyrometer is used, the uncertainty of the temperature measurement at any temperature should not exceed 10°C. 5.3 Resistance measuring instrument
5.3.1 Resistance measuring instrument for detecting precision resistance alloys and its use 5.3.1.1 It should be able to measure a change of 0.001% in the resistance value of the sample; for this purpose, a Kelvin double bridge, digital ohmmeter or other equivalent measuring instruments can be used.
5.3.1.2 The selected resistance measuring instrument is required not to affect its measurement results due to changes in ambient temperature; a qualified instrument should be able to allow a temperature change of 1C.
5.3.1.3 The measurement work is carried out under the premise that the influence of thermoelectric potential and parasitic current has been eliminated as much as possible. When these influences are small enough, the resistance value of the sample can be measured by one of the following two methods: The first method is to make the galvanometer indicate zero when the galvanometer loop is disconnected, and balance the bridge when the power is connected in the forward and reverse directions, and take the average of the two measurements as the resistance value of the sample; The second method is to make the galvanometer indicate zero when the galvanometer is connected to the measurement loop and the power is open, and take the unidirectional balanced indication of the bridge as the resistance value of the sample. 5.3.2 Resistance measuring instrument for testing materials such as electrothermal alloys 5.3.2.1 Kelvin bridge, potentiometer, digital ohmmeter or other equivalent devices can be used to complete the detection of samples with a resistance value less than 10, and Wheatstone bridge can be used to detect samples with a resistance value greater than 10; the resistance value measurement accuracy should reach 0.1% 6 Sample preparation
6.1 Sampling
6.1.1 Prepare a sample from each continuous length of the material to be tested. 6.2 Specimen size and shape
6.2.1 The size of the specimen shall meet the requirements for achieving precision resistance measurement. For wire-shaped precision resistance alloy specimens with an insulating layer, they shall be wound into a hollow coil with a diameter of not less than 50 mm; for sheet-shaped precision resistance alloy specimens, if the resistance of the specimen is not less than 0.01, the specimen may be made into a "U" shape.
6.2.2 For wire-shaped specimens without an insulating layer, they shall be wound on an insulating skeleton. It shall be noted that this shall not cause additional deformation to the specimen when the temperature changes; the tension used in the winding process shall not be too large, as long as it can ensure that the insulating wire is wound into a smooth coil, or that the bare wire coils wound on the insulating skeleton do not contact each other. 6.2.3 For thin wires made of high resistivity alloys, straight wire specimens may be used; strain shall be avoided during the sample preparation process. 6.3 Sample connection
6.3.1 For high resistance samples where the lead resistance can be ignored, the copper wire can be connected to the sample by copper welding, brazing, welding or clamping; the resistance value of this copper terminal should be less than 0.02% of the sample resistance. 6.3.2 If the sample resistance is less than 10Ω, the resistance should be measured by separating the current terminal and the potential terminal. At this time, two copper wires are connected to the two terminals at each end of the sample by means of steel welding, brazing or welding. When setting the terminal position, care should be taken to ensure that the measured potential difference does not include the voltage drop near the current connection. For sheet (strip) material samples, the distance between the inner side of each current terminal and the adjacent potential terminal should be no less than twice the width of the sample, and the terminal should be located in the middle of the width of the sample. The terminal can be made by welding on the ear cut from the sample as shown in Figure 1. For electric heating alloy wire samples, the distance between the potential lead connected by welding at each end of the sample and the adjacent current lead should be no less than one-tenth of the sample length determined by the two potential terminals. Note: The recommended length of the cut ear is 12.7mm and the width is 3.2mm. After the ear is cut, the debris at the cut should be removed. Before punching, it is best to drill two small holes in the sample with a sharp drill at the connection between the ear and the sample. Figure 1 Schematic diagram of sheet sample connection
6.3.3 The coil formed by fine metal wire usually does not have enough rigidity to support the terminal. A section of thin glass rod or ceramic rod can be passed through the coil to support the wire diagram and fix the sample connection end. 6.3.4 When the resistance value of the electric heating alloy sample is detected by Wheatstone bridge, the lead wire used is required to be made of the same material as the sample, and its resistance value should not exceed 1% of the sample resistance value. In order to avoid the temperature loss of the sample caused by the temperature difference between the inside and outside of the furnace, no matter what resistance value measurement method is used, the length of the lead wire used in the heating zone of the furnace should not be less than 50 times the minimum lateral dimension of the heating zone. 6.4 Pretreatment of the sample
6.4.1 In order to obtain a stable resistance value, the resistance alloy sample after machining must be stabilized; for manganese copper alloy, after machining, it should be kept at 140℃±5℃ for 48 hours and then cooled to room temperature. 6.4.2 After pretreatment, immerse the sample in nitric acid solution (50%) to etch away the copper film (which can be judged by the color of the sample), and then scrub it thoroughly in running water.
7 Test current
7.1 Do not select an excessively large working current to produce a significant change in the sample resistance or the indication of the measuring device to avoid the influence of thermal effects.
GB/T 4067--1999
7.2 For wire-shaped precision resistance alloy specimens, in order to experimentally determine that the selected working current is not too large, immerse the specimen in a liquid tank whose resistance value is relatively sensitive to temperature changes, and keep the selected working current unchanged until the resistance value of the specimen becomes a constant; then increase this current value by 40% and keep it unchanged until the resistance value of the specimen becomes a constant again; if the change in the above two resistance values is greater than 0.01%, it indicates that the selected working current is too large and should be reduced until the change in resistance value meets the requirements after the above test. 7.3 For sheet (strip) precision resistance alloy specimens, it is required to ensure that the power loss on the bare surface does not exceed 0.003W/cm. The method of experimentally confirming that the selected current is not too large is the same as that in 7.2, but the change of the two resistance values before and after is limited to not more than 0.001%.
7.4 For the electric heating alloy specimen, when the above experimental inspection method is used, the limit value of the change of the resistance value is 0.1%; for the alloy specimen, the test temperature is 400℃. Note: The test current for electric heating alloy materials can be determined by calculation: if the power loss of the current flowing through the specimen on the effective free surface of the specimen is less than 0.01W/cm, the effect of the test current on the resistance measurement can be ignored. For straight strip specimens and wound or bent specimens with the distance between adjacent curves greater than 5 times the maximum transverse dimension of the specimen cross section, "free surface" refers to the surface area between the two potential ends of the specimen. If the specimen is wound into a spiral or helix with the distance between adjacent curves less than 5 times the maximum transverse dimension of the specimen cross section in order to place the specimen in the furnace, or the bending spacing of the folded line formed by the front and back bending also has the above characteristics, "free surface" refers to the outer contour surface of the circular or cylindrical shape formed by the winding or folding specimen. The power loss of the measured current is calculated according to formula (4): W = PRm
W-power loss, W;
I—measurement current, A;
Rm—resistance value at the highest test temperature,. 8 Measurement procedure
8.1 Detection of electrical temperature constant of precision resistance alloy (4)
8.1.1. Connect the sample to the measuring circuit and immerse it completely in the thermostatic bath. To check the stability of the resistance value of the sample, first measure its initial value at the reference temperature (e.g. 20°C or 25°C). Raise the temperature of the thermostatic bath or transfer the sample to another thermostatic bath that is kept at the required highest temperature. After the resistance value of the sample becomes constant, record the resistance measuring instrument reading and the temperature of the thermostatic bath. 8.1.2 By cooling or transferring the thermostatic bath, lower the temperature of the sample to the next lower temperature required. After the resistance value of the sample becomes constant, record the resistance value and temperature again.
8.1.3 And so on: within the required temperature range, during the cooling process, carry out a series of resistance changes with temperature measurements. The temperature measurement interval should be 10% of the entire temperature range, or determined by negotiation between the supply and demand parties. 8.1.4 The selected temperature measurement points should be sufficient in number. In order to calculate the resistance-temperature relationship, measurements must be carried out at 3 temperatures. If the test is not carried out continuously, at least 5 temperatures of observation data are required. 8.1.5 During the continuous measurement, attention should be paid to the temperature of the resistance measuring instrument. 8.2 Detection of the average resistance temperature coefficient of precision resistance alloy 8.2.1 Except for 8.1.4, it is the same as 8.1; the measurement points should not be less than 3 points, including the reference temperature. 8.3 Detection of the average resistance temperature coefficient of electric heating alloy 8.3.1 Place the sample in the furnace and raise the furnace temperature to the specified maximum temperature. Then keep the temperature until the resistance value of the sample is constant. The "constant" here does not include the change of resistance value caused by oxidation; thereafter, the furnace temperature is lowered to room temperature in a step-by-step cooling program, and the step length should not be greater than 100°C; in this process, the stable temperature and resistance value should be measured at each step, and the time of each reading should be recorded. It is required that the resistance value read each time is at least the average value of a pair of resistance values measured by the test current in the forward and reverse directions; this forward and reverse measurement is necessary to eliminate the influence of thermoelectric potential (see 5.3.1.3). 9 Calculation of measurement results
9.1 Calculation of resistance temperature band
9.1.1 The resistance temperature constants α, B and the resistance value R at the reference temperature in formula (3). Determined by the R value measured at three temperature points with sufficient intervals. For this purpose, substitute the three groups of R and values into formula (3) to obtain three equations, and solve these simultaneous equations to obtain the values of R, α and β. 9.1.2 To simplify the calculation, R can be directly read from the plotted resistance and temperature curve. After that, two additional points are selected on the curve, of which t should be at least 5℃ lower than the reference temperature t(℃), and the second temperature t2 should be close to the highest temperature detected, and they should satisfy the following relationship:
K(tg - ti) tz to = KAt
（5）
Note: For example, if t is 10℃ lower than the reference temperature, to simplify the calculation, the value of tz should be 10℃, 20℃ or 30℃ higher than the reference temperature, respectively, in which case K==1.2 or 3 respectively.
For the convenience of calculation, K is usually an integer. If the resistance at temperature t is R1 and the resistance at t2 is Rz, then: (R1 -- R2) - K\(R/ Re)
RK(K + 1)At
β=K(RR)+(R1 -R)
R,K(K + 1)(△)?
If K—1, it can be simplified to:
β=R+R - 2R2
2R2(△t)2
9.1.3 If the resistance change relative to the reference temperature tC is measured, the above equation will have a slightly different form: Let △R1 represent the ratio of the resistance change from to to t to R2, and △Rz represent the ratio of the resistance change from to to t to R2, that is, AR1 (RR)/R2
ARz (R2 - Ro)/R.
AR2 — KAR
K(K +A
If K is 1, it can be simplified to:
KAR, +AR2
K(K + 1)(A)2
（10）
(11）
（12）
（13）)
（14）
?（ 15 )
Note: Let the set temperature of the resistance-temperature relationship be 0℃, and the relative value of resistance be the dependent variable. If the reference temperature is t. The resistance value of the sample below is R. The resistance value of the standard resistor used in the measurement is Rn, and RaRn. It is also known that the resistance-temperature relationship curve of the sample is parabolic (for example, in the range of 15-35℃, the manganese copper sample conforms to this law). There is a relationship: Pt2 = Pt2 + At + Bt2
Wherein, the ratio of the resistance value of the sample at Pt2 = 0.01℃ to the resistance value of the standard resistor at the reference temperature (℃),%; Pt2 = Pt2 -0.01℃ to the resistance value of the standard resistor at the reference temperature (℃),%. (16)
Wherein, A and B are the coefficients calculated based on the resistance measurement values at different temperatures. Based on this, a measurement method used in production inspection is: compare the resistance value of the tested sample with that of a stable resistor (resistance) placed at a reference temperature ℃ and whose characteristic parameters are known. If the two resistance values are similar, the measurement result can be directly expressed as a percentage (for example, 100.008%). If the measurement is carried out at four temperatures t1, tz, tg, and t within the temperature range where the resistance value change conforms to the parabolic relationship, the ratios of the sample resistance to the standard resistance (in percentage units) are Pl, Pz, P3, P., respectively. The constants A and B and the resistance temperature constant can be calculated by the following formula: 1 2 PP
t2 ti
GB/T 4067-1999
The relationship between constants A, B and the resistance temperature constant is: P2 P
— B(t2 — ty)
tz — ti
α=（A+2Bro)/100
β= B/100
9.2 Calculation of peak temperature or extreme temperature
According to formula (3), the temperature corresponding to the maximum (peak) or minimum on the parabolic resistance temperature curve can be obtained: tn = to
Where: tm—peak temperature or extreme temperature, C; to—reference temperature, C;
-primary resistance temperature constant, ℃
βSecondary resistance temperature constant, ℃2.
9.3 Calculation of resistance temperature factor and average resistance temperature coefficient..(18)
**·( 19)
( 20 )
( 21 )
9.3. 1Complete the calculation of resistance temperature factor according to formula (1); in the specified temperature range, complete the calculation of average resistance temperature coefficient according to formula (2). 9.4 Temperature-resistance curve and singular points
9.4.1 Using the room temperature resistance value after cooling as the reference, plot the resistance versus temperature curve; mark the time interval between successive readings on the graph corresponding to the curve; determine the accurate resistance-temperature characteristic parameters of the material under test based on the cooling curve (see 9.1.2, 9.2, and 9.3). 9.4.2 If it is found that the curve is not smooth at certain points, perform another temperature cycle; re-measure the temperature and corresponding resistance value at intervals close to 25°C in the abnormal area.
10Test report
Test report on resistance temperature constant measurement
The test report shall include the following contents:
a) Sample brand;
b) Description of the material and its insulation condition;c) Geometric dimensions, potential terminal distance and approximate resistance value of the sample;d) Table recording the resistance-temperature relationship;e) Temperature of the measuring device and room temperature at the beginning and end of the measurement;f) t and △R values used for numerical calculation of α and β;g) Calculated values of resistance temperature constants α and β, with numerical rounding in accordance with GB/T8170, rounded to 0.1×10-bit;h) Sample temperature or peak temperature within the measurement range when the sample resistance value does not change with temperature. 10.2 Test report on average temperature coefficient of resistance The test report shall include the following:
a) Sample brand;
b) Description of the material and its insulation condition;
c) Geometric dimensions of the sample and its approximate resistance value;
d) Table recording the resistance-temperature relationship;
e) Temperature of the measuring device and room temperature at the beginning and end of the measurement;
f) The measured value of the temperature coefficient of resistance, in units of 1×10-6℃-1, and the numerical value shall be rounded off in accordance with GB/T8170. 11 Accuracy and deviation
11.1 Accuracy and deviation of resistance temperature constant measurement 11.1.1 The technical level of the instrument and the operator plays a great role in determining the quality of the measurement; this method cannot yet give exact data on the accuracy and deviation of the resistance temperature constant measurement. GB/T4067--1999
11.2 Accuracy and deviation of average resistance temperature coefficient and electric heating alloy detection 11.2.1 The reproducibility of the change of resistance with temperature depends mainly on the uniformity of the temperature in the sample and secondly on the cooling rate; for nickel-chromium alloys, the faster the cooling, the smaller the resistance change. 11.2.2 The accuracy of this test method is within ±2%. 11.2.3 Based on the reasons stated in Article 11.2.1, the deviation cannot be determined. 102
GB/T4067-1999
Appendix A
(Suggestive Appendix)
Optional Calculation Methods and Supplementary Provisions
A1 Another useful and optional method for calculating the α and β values is: for a given manganese copper sample, when its resistance value R. is close to the standard resistance value R, if its resistance values at three different and appropriate temperatures (one of which is at the reference temperature) are known, then substitute them into formula (3) to form two equations; solve the equation group and obtain the α and β values after sorting: Pa- Po- Pm- Po
t. - t.
tm - to
te — tm
th - to
β(tn — to)wwW.bzxz.Net
Where: P. The relative difference between the sample and the standard resistance when the temperature is tn (℃), 1X10-\;P-the relative difference between the sample and the standard resistance when the temperature is tm (℃), 1×10-°;P. --The relative difference between the sample and the standard resistance when the reference temperature is to (℃), 1X10-;α, β-resistance temperature constant, α unit: 1×10-6℃-β unit: 1×10-6℃-2A1.1 Peak temperature (tm, C):
tmax = to —α/(2β)
A1.2 The (instantaneous) temperature coefficient (TC, 1×10-6℃-1) at any temperature is: TC = α + 2β(t - to)
A1.3 During the resistance measurement process, the temperature should be controlled within ±0.2C. ·（A1）
（A3）
A1.4Measure and record the relative difference between the sample and another resistor, expressed in parts per million, and let Pm and P. be the relative differences corresponding to tm.
A1.5The resolution value of manganese copper wire resistance measurement should not be greater than 1X10\, and the resolution value of manganese copper sheet resistance measurement should not be greater than 5×10-6.
A1.6After obtaining the resistance values at three different temperatures, substitute the corresponding groups into the relationship between α and β to obtain the α and β values. A1.7 If there are special requirements for the determination of α and β values, measurements should be performed at four temperature points; first, three of the four "temperature-resistance relative difference" arrays are selected to calculate the α and β values; in the second calculation, three of the four arrays are selected, including the array that was not selected in the first calculation, to obtain the second set of α and β values; the calculation of α and β values using different arrays helps to avoid errors. The difference between two α or β values cannot exceed 10%. 103
Tip: This standard content only shows part of the intercepted content of the complete standard. If you need the complete standard, please go to the top to download the complete standard document for free.