Calibration Specification for Absorbing Clamp in the Range of 30MHz to 1.0GHz
Some standard content:
National Metrology Technical Specification of the People's Republic of China JJF1155—2006
Calibration Specification for Absorbing Clamp in the Range of 30oMHz to 1.0GHzPromulgated on 2006-05-23
Implementation on 23rd
National General Administration of Quality Supervision, Inspection and Quarantine issued JJF1155—2006
Calibration Specification for Ahsorbing Clamp in the Range of 30MHz to 1.0GHzJJF1155—2006
This specification was approved by the General Administration of Quality Supervision, Inspection and Quarantine on May 23, 2006, and came into effect on August 23, 2006.
Responsible unit: National Radio Metrology Technical Committee Drafting unit: China National Institute of Metrology The National Radio Metrology Technical Committee of this specification is responsible for the interpretation.
Main drafter of this specification:
Wang Jilong
Participating drafter:
Guo Ruimin
Shen Qingfei
JJF 11552006
(China National Institute of Metrology)
(China National Institute of Metrology)
(China National Institute of Metrology)
(China National Institute of Metrology)
(China National Institute of Metrology)
(China National Institute of Metrology)
(China National Institute of Metrology)
References·
3 Terms and units of measurement…·
Absorptive clamp·
Absorptive clamp insertion loss
Absorptive clamp correction factor
4 Overview
Use of absorber drill
4.2 Structure of absorber clamp…
5 Metrological characteristics
6 Calibration conditions
6.1 Environmental conditions
6.2 Main equipment used for calibration
Calibration items and calibration methods
Appearance and normality inspection
Calibration method
Parameter setting of calibration equipment
7.4 Improvement of calibration method
8 Expression of calibration results
9 Time interval for recalibration
Appendix A Contents of calibration record
Appendix B Contents of the inner page of calibration certificate
JJF 1155--2006
Appendix (1) Working principle of absorbing clamp and emission equivalent circuit record D Uncertainty evaluation example
(3)
(4)
1 Scope
JJF 1155--2006
30MHz～1.0GHz Absorption Power Clamp Calibration Specification This calibration specification is applicable to the calibration of absorptive power clamps ENH (absorption clamps) in the frequency range of (30～1000) MHz that meet the requirements of GB/T 6113.1-1995 and GB/T 6113.2-1998 standards,
References
GB/T 6113.1
GB/T 6113,
GB/T 4365
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, care should be taken to use the currently valid versions of the references. Rhing clamp equipment with power line fittings, whose resistance is measured by the maximum energy provided by the lines (only the part outside the equipment) and absorbing the excitation energy provided by the lines. This power is close to the maximum power that can be absorbed when the absorbing device is placed in the lead wire. This absorbing device is called an absorbing clamp or a ferrite clamp. Y
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3.2 Insertion loss of the absorbing clamp
The insertion loss of the absorbing clamp is the loss of the device in this specification, expressed in decibels, symbol dB. 3.3 Correction factor for absorption The correction factor for the absorbing clamp is the difference between the insertion loss of the absorbing clamp and 17, expressed in decibels, symbol B. 17 is the approximate value of 10log50, which is the conversion factor between dB (uV) and dB (pW) in the 500 measurement system: 4 Overview
Use of Absorbing Clamps
JJF 1155—2006
The absorbing clamp can be used to measure the radiation from the leads in the frequency range of (30-1000) MHz. Not only the power lines of the equipment (such as shielded or unshielded leads) also radiate energy in the same way as the power lines, but the absorbing clamp can also measure these lines:
The absorbing clamp is only applicable to the interference measurement of some types of equipment, which depends on the construction and size of those equipment. Strict measurement methods and applicable scopes should be specified for each type of equipment. If the size of the equipment under test (hereinafter referred to as EUT, excluding connecting leads) is close to 1/4 wavelength of the measurement frequency, then direct housing radiation may occur. Therefore, the absorbing clamp method is not suitable for evaluating the full radiation capability of the EUT. This method is usually suitable for small EUTs and the frequency range of (30300) MHz.
4.2 Structure of the absorbing clamp
The absorbing clamp consists of three parts:
a) Broadband RF current transformer: A coil of coaxial cable is wrapped around two or three ferrite rings, which acts as an electric The role of the current transformer is to induce a signal into the coil from all the RF current flowing through the test cable combined with the ferrite ring:
b) Broadband RF power absorber and stabilizer of the test equipment lead: an absorption part is composed of more ferrite rings stacked together, located below the test cable away from the emission source, the purpose is to stabilize the RF impedance of the test cable and reduce its dependence on the remote terminal load;) Absorption sleeve: the part of the absorber covering the cable sheath of the current transformer, that is, the part attached to the ferrite ring It increases the common mode impedance of the cable, thereby reducing the effect of any changes in this impedance. It can be used to reduce the RF current on the long side of the coaxial cable from the current conversion to the measurement receiver via parasitic capacitance coupling through the transformer to the test cable.
Figure 4. Schematic diagram of the absorbing clamp structure
A-Test equipment: B, B-Test leads: -Central current transformer: T)-Power absorber and positive impedance stabilization part; E-Absorbing sleeve: H-Central cable between current transformer and transmission connector 5 Metering characteristics
Absorption attenuation (insertion loss)
According to the calibration method required by this specification, the insertion loss value is: (1422) cdB. Note: This specification does not calibrate the output power response characteristics and impedance characteristics. 6 Calibration conditions
Medium current converter
Two rings
Absorption clamp reference point
J.IF1155—2006
640 mm±40 tm
34 rings
Figure 4.2 Schematic diagram of the absorption clamp structure after performance collection B-test lead; C-current transformer; D-power absorption and impedance stabilization part; F-absorption sleeve; 1-a pair of metal semicircular cylinders; 2-insulating tube: 3-coaxial connection 6.1 Environmental conditions
Temperature: (2315)℃
6.1.2 Relative humidity: ≤80%
6.1.3 AC power supply: (220+22)V, (50±2)Hz6.1.4 There is no electromagnetic interference and mechanical vibration that may affect the calibration work in the surrounding area6.2 Main equipment used for calibration
6.2.1 Spectrum analyzer or EMI receiver
6.2.1.1 Spectrum analyzer (with built-in tracking source) a) Frequency range: (30-1000)MHz; b) Tracking source output power: 0dBm;
c) Measurement mode: maximum hold.
6.2.1.2EMT receiver (built-in tracking source) a) Frequency range: (30~1000) MHz
b) Tracking source output power: ≥0dBm;
c) Measurement mode: Maximum value hold.
6.2.2 Electric slide rail
The length, height and maximum moving distance of the slide rail should be greater than 6m, 0.8m and 5m respectively. The speed of the pulley carrying the absorbing clamp can be adjusted in a certain range. The transmission part needs to use a low-radiation motor and a rubber toothed belt. The limit switch is installed at both ends of the rail, which must meet the requirements of electromagnetic environment, mobile positioning accuracy and safety during calibration. 6.2.3 Insulated copper wire for calibration
JJF 1155—2006
The commercially available single-strand copper wire with an insulating sheath for electricians has a cross-sectional area of 4inm? 6.2.4 Coaxial fixed attenuator
a) Frequency range: (30-1000) MHz; b) Impedance: 50Ω;
e) Port voltage standing wave ratio (maximum): 1.15:1; d) Attenuator: 6d3 and 10dB.
HOHSNIHSTH
7 Calibration items and calibration methods
7.1 Appearance and normal working inspection
The calibrated absorption clamp should be complete with necessary accessories (6dB attenuator and receiving power) 7.1.1
The calibrated absorption clamp should be intact
7.1.3 The calibrated absorption clamp should not be significantly changed after the calibration device is connected. The calibration system is calibrated after preheating
7.2 Calibration method
Calibration arrangement
GB/T 6113-1996 gives the characteristics and meaning of the two methods of absorbing clamps. Discrete frequency method is selected when the accuracy of the calibration result is high. When the RF signal generator is moving, a rope can be used to pull the receiver and calibration lead. The calibration method is shown in Section 27.2.2.2 of the specification. The mechanical explosion of the calibration lead is moved. The receiver reading should have a small number of frequency points, such as inter-laboratory comparison or arbitration detection. Slowly move along the rail to maintain the EMI receiver. In the absence of electrical equipment, personnel must stay as far away from the absorbing clamp as possible. Use a spectrum analyzer with built-in tracking source or test receiver. Move the absorbing clamp once to obtain many frequency points and daily calibration of the absorbing clamp. The input loss of the frequency point can be adjusted according to the test accuracy. 7.2.3 Calibration steps 7.2.3.1 The absorbing clamp calibration device consists of an insulated copper lead with an effective cross-section of (1~2)n2 and a length of 6m, a grounded metal plate not larger than 2.5m×2.5m (or the wall of the shielding room), and a non-metallic workbench with a guide rail. One end of the lead is connected to Connected to the 50 connector core, the connector is mounted on the grounded metal plate so that only the center connector protrudes. The other end of the lead passes through the current transformer of the absorbing clamp and the end is open. 7.2.3.2 As shown in Figure 7.1, in the range of (30~-1000) MHz, two coaxial cables a and b are connected according to the solid line. At each frequency (see Table A.1 and Table A.2 in Appendix A), the absorbing clamp moves along the lead from the floor
Measurement receiver
JJF1155-20X06
Figure 7.1 Calibration layout of the absorbing clamp
Signal generator
E tracking source||tt| |dBiAtt
W--calibration line; C--current transformer; 1)--power absorber and impedance stabilizer part: upper--absorption sleeve; F--additional absorption clamp, frequency requirement is less than 50MHz; (--Fantong connector for connecting calibration line and attenuator; C2--coaxial connector connected to the coaxial cable inside the absorption clamp: a connecting receiver cable and matching hand-held axial connector: a coaxial cable connecting the absorption clamp and the measurement receiver; b--coaxial cable connecting the signal generator and attenuator; Att--10uR coaxial attenuator; Ci, (3, a, b, Att--represent (, (, b and At1 placed on the dotted line respectively. At this time, the signal generator and the measuring receiver are directly connected, and the reading of the measuring receiver only includes the attenuation on the attenuator and the coaxial cable: [--At this position] the instrument indicates the maximum, and the absorbing clamp is inserted together with the measured wire: 1--The constant output when the signal generator carries a 50Ω load; 2--After connecting the absorbing clamp, the maximum indication of the measuring receiver: 2'When the signal generator is only connected through the attenuator and the coaxial cable (according to the rate line), the measuring receiver indicates: F--Multiple ferrite absorption rings, that is, the distance from the beginning of the casing shield to half the wavelength is mountain (because the tracking source outputs a sine wave during actual calibration, the positive and negative half cycles are symmetrical. Therefore, under normal circumstances, the maximum reading on the receiver can be obtained by moving a distance of more than 1/4 wavelength). Write down the maximum indication α of the EMI receiver and fill it in the corresponding columns of Table A.1 and Table A.2 in Appendix A. 7.2.3.3 Keep the level of the signal generator or tracking source constant, and then connect the two coaxial cables mentioned above by the dotted line, as shown in a and 6 in Figure 7.1, and write down the receiver indication α and fill it in the corresponding column of Table A.1 and Table A.2. Minimum insertion loss L (dB) Formula (7.1) calculation: L = a
7.2.3.4 Repeat step 7.2.2.2 within the frequency range required for the absorption clamp calibration. Figure 7.2 gives an example of the calibration curve. Under normal circumstances, the measured insertion loss value should comply with the provisions of Article 5. During calibration, personnel should be 1.25m away from the cable.
7.2.3.5 The limit value of interference power in the electromagnetic compatibility standard is in d (pW). The EMI receiver voltage reading dB (μV) needs to be converted into power expressed in dB (pW). The standard EMI receiver input impedance is 50QJJF 1155--2006
Based on the relationship between power (W), voltage (V) and impedance (2), the power expressed in logarithmic form can be obtained: P[dB(pW)] = U,[dR(μV)) + KLdB(pWiV) I+ L.(dB) K in formula (7.2) is the correction factor of the absorption clamp, which can be expressed by the following formula: K:dB(pW/μV)J -L(dB)-17[d3(pW/μV)](7.2)
The conversion factor between d3 (uV) and d (pW) in the 502 system is -17dB. Strictly speaking, the correction factor only applies to the absorbing clamp. When the output cable is connected to the absorbing clamp through a 6B attenuator and this device, if there is no attenuator or different cables are used, the correction factor may be different. 7.3 Parameter settings of calibration equipment
7.3.1 Discrete frequency method
7.3.1.1 Signal source and spectrum analyzer parameter settings a) Start frequency: 30MHz or 300MFIz
b) Stop frequency: 300MHz or 1000MHz) Reference level: 97dB (μV)
d) Input attenuator: 10dB
e) Vertical division: [0dB/Div
f) Resolution bandwidth: 5MHz
9) Video bandwidth: 1MHz
h) Signal source frequency: set within the range of (30-1000) MHs according to customer requirements i) Signal source output level: 97dB (rV
j) Frequency sweep mode: Maximum value hold
7.3.1.2 Slide rail controller parameter setting
a) Minimum position: 0cm
b) Maximum position: 400cm
) Travel speed: The minimum speed set by the slide rail controller III 7.3.1.3 Movement of the absorbing clamp
At each frequency point, the distance from the reference plane is 0.15m is the reference point, and the moving absorption clamp exceeds 1/4 of the lowest frequency wavelength and is greater than 400cm, and goes back and forth once. 7.3.2 Sweep frequency method
7.3.2.1 Parameter setting of spectrum analyzer and slide controller In the parameter setting, except that the tracking source is used to replace the signal generator, the rest is basically the same as that of discrete frequency method calibration. 7.3.2.2 Movement of absorption clamp
In the whole frequency range, 0.15m is the reference point, and the moving absorption clamp exceeds 1/4 of the lowest frequency wavelength and is not greater than 400cm, and goes back and forth once. 20
JJF1155--2006
Frequency: MHz
Figure 7.2 Example of absorption clamp calibration curve
The wave crest points measured by the Changchuan absorption clamp are more than one, and the receiver indication given by the wave crest point closest to the calibrated lead end of the 502 connector is the largest. Practice has proved that compared with the first peak, the insertion loss given by the second peak is about 1dB larger. In some actual situations, it is convenient to measure the second peak. This situation is also suitable for the calibration of the absorption clamp. Curve A and Curve B in Figure 7.3 are examples of curves for calibrating the absorption clamp when measuring the first peak and the second peak respectively. P
Correction/dB (pw)
7.4 Improvement of calibration method
2nd wave peak
Bend B
1st wave
Frequency/MHz
Obtained power = measured receiver reading·Correction coefficient Figure 7.3 Absorption clamp calibration curve
Figure 7.4 shows the improved calibration arrangement, which has three differences from Figure 7.1: first, a 6 coaxial attenuator is added at the output connector of the absorption clamp; second, the receiving cable is required to be kept as perpendicular to the calibration lead as possible, and several clamp-type ferrite rings are attached to the cable; finally, a non-metallic central guide matching the calibration lead is added at each end of the absorption clamp. The reasons for these three improvement measures are explained in detail in Appendix D Uncertainty Assessment Examples and will not be described here. The second absorption stomach
Ferrite ring
Lead section: 4mm
The shuttle line should be pulled as far as possible
JJE11552006
Receiving cable
Non-central locator
6 attenuator
Calibrated absorption clamp
Sliding reference point
The receiving cable should be as close as possible!
Calibration line vertical
Spectrum analyzer input
Spectrum analyzer with tracking source
Figure 7.4 Improved absorption error calibration arrangement
Zero reference plane
Calibration lead
8 Calibration result expression
N-type connector
Center conductor and calibration lead welding
Figure 7.5 Schematic diagram of vertical reference plane
N-type axial connector
Connector +10dB
Coaxial attenuator
42.5 m×2.5 m
Metal vertical
Reference plane
Tracking source output
N-type female connector
10dB coaxial attenuator
Coaxial cable with N-type (I1) coaxial connector
The calibrated absorbing clamp should be issued with a calibration certificate. The calibration certificate should include sufficient information, such as the name and location of the calibration laboratory, the number of the calibration certificate, the name and address of the sending unit, the name, model, manufacturer, serial number of the calibrated absorbing clamp, the date and location of calibration, the name of the technical specification based on which the calibration is based, the traceability and validity of the measurement standard used in this calibration, the calibration results and their measurement uncertainty. The contents of the calibration certificate are shown in the appendix.
9 Recalibration time interval
The sending unit can decide the recalibration time interval based on the actual use of the absorbing clamp. The recommended recalibration time interval is 1 year. The repaired or adjusted absorbing clamp should be calibrated before use.
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