This standard applies to the measurement of the average value of the real part of the characteristic impedance of a coaxial pair of manufacturing length by the resonance method. GB 5441.5-1985 Communication cable test method Coaxial pair characteristic impedance real part average value test resonance method GB5441.5-1985 standard download decompression password: www.bzxz.net

1 Scope of application
National Standard of the People's Republic of China
Test methods for communication cableCharacreristic impedance test of coaxial patrResonance method
The standard applies to the resonance method used to measure the mean value of the real part of the characteristic impedance of the coaxial pair of the longest manufacturing length. UDC621.315.2
:621.39:621
.317.3.08
CB 5441,5—85
The test frequency range is 0.16～10MHz. Under the conditions permitted by the test equipment, the test frequency range can be expanded. The test accuracy can reach 0.2%. www.bzxz.net
2 Test equipment
The wiring diagram of the test is shown in Figure 1 and Figure 2
Figure 1 Bridge harmonic test wiring diagram
National Bureau of Standards 1985-09-29 Issued
1986-06-01 Implementation
Figure: G—Electric power supply device:
B—High impedance (nano) bridge;
1—Frequency selection level meter:
"——Mathematical frequency meter;
C—Tested pair:
GB 5441.5 -85
Figure 2 Compensation test circuit diagram
Two variable attenuation boxes with different models and specifications, A, used as attenuators: -74122;
W-1002 non-inductive electric devices.
The test instrument should meet the following requirements:
2.1 Level oscillator: The frequency drift should not be greater than 10 (continuous 1 hour) within the specified test frequency range, and the output voltage should be 10dB~2.2 Frequency selection device: The sensitivity should not be lower than 90dE (excluding the data meter) within the specified test frequency range. 2.3 Main step impedance (admittance) electrical correction: The accuracy is ±1% of the measured value. 2.4 Digital frequency meter: The number of digits displayed should be no less than 6, and the frequency stability should not be lower than 1.5×107/24h. 2.5 Attenuator: The total attenuation of each gear should not be less than 40dB, and the attenuation of the smallest gear should be at least 0.1dB. The applicable frequency range of the attenuator includes all the frequency points required for testing. 3 Sample preparation
The sample is a finished cable of manufacturing length.
4 Test steps
.1 According to G5441.2--85 "Standard Test Method for Specific Capacitance Test, Electromagnetic Method", determine the measured voltage of the tested cable! (1)
GB5441.5-85
4.3 When testing with the connection in Figure 1, the following steps should be followed: 4.3.1 Connect the instrument as specified in Figure 1, and turn on the power supply to preheat without connecting the sample until the instrument is stable. 4. 3.2 Set the resistance (conductance) and inductance (capacitance) of the bridge to the "zero" position, adjust the output frequency of the oscillator to the value estimated by formula (1) when n-2.4,6,\,n, and use the zero half balance device of the bridge to adjust the zero balance after the meter selects the frequency.
4.3.3 Short-circuit one end of the measured axis pair and connect the other end to the test end of the bridge. Repeatedly adjust the frequency of the oscillator and the current (conductance) of the bridge and gradually increase the sensitivity of the level meter to minimize the reading. 4.3.4 Read the measured value of the harmonic frequency from the frequency i:1 and record the value of n. 4.3.5 Change the confirmed value , repeat the steps specified in Articles 4.3.2 and 4.3.3, measure and read the measured values ​​fnm and n of each harmonic frequency when the cable terminal is short-circuited.
4.: When testing with the wiring in Figure 2, follow the steps below: 4.4.1 Connect the test system as specified in Figure 2, and make the total length of the A, branch drop and A, branch connection equal. After checking that everything is correct, turn on the power and preheat the instrument to stabilize.
4.4.2 Estimate the point attenuation of the sample under test at the highest test frequency, and place the attenuator A2 at any position greater than this value. 4.4.3 Connect the sample under test, adjust the input frequency of the carbon oscillator, and at the same time Use the frequency selection level to track the frequency selection. At the frequency points near the frequency estimated by formula (1), select the frequency number of the desired test with a frequency of F250kHz. Repeatedly adjust the variable attenuator A and the input rate of the oscillator to make the meter indication the lowest. Then adjust the fine adjustment potentiometer to make the meter sensitivity reach about -100dB. Read the frequency/n from the meter and record the value of number n. 5 Test results and calculations
The test results are obtained by the following formula:
Wuzhong: The real part of the characteristic impedance of the sample is the average dimension, n——who photographed! number, n -2.4,6,...-,n;C is the capacitance of the measured pair, u;
——the actual resonance of the sample, MHz.
should be calculated according to the test system of Figure 1: fh =fnm[1-(
Formula: .-the actual resonant frequency of the sample, MI12; fnn-
-the resonant frequency of the sample to be tested, MHz; the wavelength of the test frequency on the sample, km: α-
17.372 yuan
-the attenuation of the sample corresponding to the measured frequency, dB/km, which can usually be obtained by taking the nominal value of each country's axis pair at 1MHz and converting it to aV. When testing according to the test system in Figure 2, fn-fnm
6 Notes
(2)
(3)
6, 1 If the measured fm deviates greatly from the value estimated by formula (1), the oscillator output must be set at a frequency of , and the steps of 4.3.2 and 4.3.3 must be repeated for retesting. 6.2 The inner and outer conductors of the short-circuit end of the sample must be kept eliminated to ensure good short-circuit contact. 3 During the high-frequency test, the resonance number is easy to be wrong, and it is necessary to count point by point to obtain the true value of the resonance number. GB541.5-8
This standard was originally issued by the Shanghai Institute of Mechanical Engineering of the Ministry of Industry of the People's Republic of China. This standard was originally issued by the Shanghai Institute of Mechanical Engineering of the Ministry of Industry.
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