GB 5441.10-1985 Test methods for communication cables - Coaxial pair unrolled length measurement - Sine wave method

This test method is based on the use of precision measurement to determine the f∞, B0 values ​​of the coaxial pair, and then the resonance frequency and the DC resistance of the inner conductor of the coaxial pair in the same cable are measured to calculate the unfolded length of the coaxial pair under test. The test frequency is above 250kHz. According to the consistency of the relative dielectric constant of the coaxial pair, the test accuracy can be between 0.1% and 0.01%. GB 5441.10-1985 Communication cable test method Coaxial pair unfolded length measurement sine wave method GB5441.10-1985 standard download decompression password: www.bzxz.net

1 Scope of application
National Standard of the People's Republic of China
Test methods for communication cableMeasurement of actual length of coaxial pairSine wave method
UDC 621.315.2
: 621. 39 : 621
.317.3.08
GB5441.10—85bzxz.net
This test method is based on the use of precision measurement to determine the /, B. value of the coaxial pair, and then the resonance frequency and the DC resistance of the inner conductor of the coaxial pair in the same cable are measured to calculate the length of the coaxial pair under test. The test frequency is above 250kIIz. According to the consistency of the relative dielectric constant of the coaxial pair, the test accuracy can be between 0.1% and 0.01%. 2 Test equipment
The test system wiring is shown in Figure 1. The test instrument should meet the following requirements: 2.1 Oscillator; The input impedance is 752, and the mismatch attenuation of the 759 resistor (including the lead) should not be less than 32dB, and it can lock the frequency in 0.1MHz or smaller steps. The frequency stability should not be less than 1×10-±10Hz2.2 Frequency selection: The input impedance is 75, and the mismatch attenuation of the 752 impedance (including the lead) should not be less than 132dB. 2.3 Digital frequency it: There should be a wave device that can display five digits, and the frequency stability should not be less than =1.5×10~7/24h. 2.4 Compensation network: The component specifications and wiring are shown in Figure 1. The entire network must be well shielded. 2.5 High-frequency impedance (admittance) bridge: When there is no compensation network, a high-frequency impedance (admittance) bridge with an accuracy of 2 is used instead. At this time, the test system adopts the connection shown in Figure 2 of GB5441.5--85 "Common method cable test method coaxial pair characteristic impedance real part average value test resonance method".
2.6 Test lead: The impedance is the same as the coaxial pair to be tested. When testing multiple coaxial pairs with the same structure, a quality test line must be used. Test lead
Connect the coaxial pair to be tested
Compensation Deng Road
Figure 1 Compensation method to test resonant frequency
G--Oscillation; D--Selection Level Meter: "--Digit Frequency Meter National Bureau of Standards 1985-09-29 Issued
1986-06- 01 Implementation
GB5441.10—85
R, W, W in the figure are group numbers, which can be changed according to the specific conditions of the object being measured. 3 Sample preparation
The sample is a finished cable of manufacturing length, which can be a single or several interaxial pairs connected as a sample. 4 Test steps
4.1 Precision measurement
Take 4 to 5 finished cables, flatten them, and use a measured steel tape to measure them. The length of each measurement should not be less than 30㎡, and the measurement error should not be greater than 1×10. Use the measurement results and the coaxial pair twisting constant to calculate The unfolded length of the coaxial pair of the cable is obtained. The twist constant of the coaxial pair is calculated by the following formula: (1)
The unfolded length of the coaxial pair is:
Wherein — the unfolded length of the coaxial pair, m
[m---the basic length of the cable, km;
D,——the average diameter of the cable core layer where the coaxial pair is located, mm, H-the twist pitch of the coaxial pair, mm:
The twist constant of a coaxial pair.
4.2 Calculation parameters and B.
4.2.1 According to GB3048.4-83 "Diameter of the Conductive Core of Wires and Cables According to the "Current Resistance Test Method", the DC resistance of the inner conductor of each coaxial pair of samples is measured, the average value is calculated, and converted to the half-mean value R of each unit at +20°C. 4.2.2 Calculate the equivalent relative dielectric constant er value of the inner and outer conductor diameter ratio D/value of the coaxial pair. 4.2.2.1 Method,
a, estimate the gate/d value of the coaxial pair according to the design requirements and process parameters, and then take the measured average value of the end impedance 2. The average value R of the DC resistance of the inner conductor of the coaxial pair is substituted into formula (3) to estimate the estimated value of the equivalent relative dielectric constant ε of the coaxial pair. Ze
where ：Z.
60_1m-
The average value of the real part of the characteristic impedance of a coaxial pair (when the non-uniformity of the coaxial pair is less than 3%, the half-mean value of the actual measured value of the end impedance measured by the pulse method can also be used instead), D-
-Inner diameter of the coaxial outer conductor, mm:
-Outer diameter of the coaxial inner conductor, mr,
Equivalent dielectric constant of the coaxial pair,
The characteristic impedance frequency value specified in the first product standard. 1.2/4.4mm type coaxial pair, at =1MHz, 2.6/9.5mm type coaxial pair, " =2.5MH-
Then use the Dd and e values ​​in formula (4) to calculate the parameters B. f
(Milz.km)
GB5A41.1D—85
. The calculation result is taken to five significant figures, and the path is taken to four significant figures. 4.2.2.2 Method..
a According to the provisions of GB5441.2-85 "Communication Cable Test Method Working Capacitance Test Bridge Method", accurately measure the upper capacitance of each coaxial pair, calculate the average value, and convert it to the average value of the working capacitance of each result (.b. According to the provisions of GB5441.5-85 "Communication Cable Coaxial Pair Characteristic Impedance Real Part Average Value Test Resonance Elimination", measure the real part average value of the characteristic impedance of each coaxial pair, and calculate the average of the real part average value of the characteristic impedance of each coaxial pair. When the impedance nonuniformity of the coaxial pair is less than 3%, the average value of the terminal impedance measured by the pulse method can also be used instead. c: Substitute R, Ca, and Z into equation (6)
Alnr+ B(1 -
Formula: A=
V2·10-3
)-Z~Inx =0
Solve equation (6) to obtain D/d, and substitute it into equation (7) to obtain e-18x10a0lm
Where: z,
-the average value of the real part of the characteristic impedance, 2; - the average value of the working capacitance of the coaxial pair, nF/km, Ra——the average value of the DC current of the inner conductor (20°C), /km; -2.6/9.5mm coaxial pair is 2.5MHz;
1.2/4.4mm coaxial pair is 1MHz.
d. Substitute the values ​​of D/d and e into formula (4) and (5) to obtain the values ​​of f and B. 4.8 Measure the resonant frequency of the coaxial pair under test
4.3.1 Estimate the resonant frequency according to the following formula:
Where: Jn——spectral resonance frequency, MHz;
real part of the characteristic impedance of the coaxial pair, which can be taken as the theoretical value, 2; Z
test length coaxial pair working capacitance can be taken as the theoretical value, nF; Cf
-resonance number, which can be 2, 6, 10, 14.*.
4.3.2 Connect the test system according to Figure 1, turn on the power supply after checking that it is correct, and preheat the instrument to stabilize. 4.3.3 Connect the coaxial pair that has been precisely measured for testing. Starting from low frequency, while adjusting the oscillator input frequency, use the level meter to follow the frequency selection. At the frequency points where the serial number n is 2, 6, 10, and 14, the frequency selection meter's pointer shows the lowest point. Select a frequency higher than the table for testing.
1.2/4.4mm in phase
2.6/4.5mml3 input pair
Appropriately adjust the potentiometer of the compensation network to reduce the level of the lowest point, and repeatedly adjust the frequency compensation potentiometer to make the selector meter GB 5441:10-85
indicate the lowest (--usually up to about -1umdB). Read the frequency fn from the frequency meter and record the serial number. .4 Measure the point resistance of the conductor of the same rail pair under test, 74.5 Correct the value of f and B calculated by formula (4) 4.5.1 Calculate the expansion length of the measured axis pair measured by the following formula! ; n
and calculate the average length of each coaxial pair of the sample mountain "Ret
4.5.2 Calculate: 1 and the percentage error of the precision measurement of the extended length in Article 4.1 and the total percentage error of 4 to 5 precision measurement cables. Use this total percentage error correction value to find f, and then use the f value to find the e value and calculate B. If the calculated B value is inconsistent with the driving value, the B value should be substituted into formula (9) and the reverse calculation should be carried out. Test results and calculations
5.1 The test results are calculated as follows:
Ix =lxy-ty
Where: "y--the extended length of the coaxial pair under test including the electrical length of the test lead, m; the electrical length of the test lead, m
-the extension of the coaxial pair under test, m.
5.21 The following formula is used for calculation:
ixy =n
5.8 1y is calculated as follows
I, =I xa +I xu.-Ia= +1
Formula: x, 1--the expanded length of the tested pair A, B including the electrical properties of the coaxial lead, m, tAB--the expanded length of the A, B axis pair, m; Fu
-the length of the coaxial pair for loop connection, m (the structure of the coaxial pair for loop connection is the same as that of the coaxial pair for test). When the lengths of the coaxial pairs of the samples are inconsistent, the measurement value of the shorter coaxial pair of the samples shall be taken. 6 Precautions
6.1 When the compensation network is terminated and the high-frequency impedance (admittance) bridge is used to test the resonant frequency f, Sections 4.3.2 and 4.3.3 of this standard shall be carried out in accordance with Section 4.1 of GB5441.5.
6.2 When the process, structure, and material of the manufacturing process of the coaxial pair are changed, the steps of Sections 4.1 and 4.2 shall be repeated. Additional Notes:
This standard was proposed by the Ministry of Machinery Industry of the People's Republic of China, and was drafted by the Ministry of Machinery Industry's Marine Cable Research Institute. The drafter of this standard was Zhang Shuju.
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