Current probe calibration device and calibration method

Abstract

The invention relates to a current probe calibration device and calibration method. The device comprises a network analyzer, a calibration clamp, a non-conductive support and an adapter. The non-conductive support is used for fixing the calibration clamp. The input end of the calibration clamp is connected with a port PORT1 of the network analyzer, and the output end of the calibration clamp is connected with a load; a to-be-calibrated current probe is clamped on a central lead of the calibration clamp; and the adapter is used for connecting the output end of the current probe to be calibrated with the port PORT2 of the network analyzer. The calibration method comprises the following steps: setting and calibrating the network analyzer; assembling a calibration clamp; installing a current probe to be calibrated; starting a network analyzer for scanning, and recording amplitude data of the parameter S21; and the transmission impedance of the current probe to be calibrated is calculated according to a formula Zt = S21 + 34, and calibration is completed. The problems that an existing current probe calibration method is complex and large in error are solved.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic compatibility testing technology, specifically to a current probe calibration device and calibration method. Background Technology

[0002] As a core tool in electromagnetic compatibility (EMC) transmitted interference testing, the current probe measures the radio frequency current on cables in a non-contact manner. The accuracy of its performance parameters directly affects the reliability of the test results. Currently, current probe calibration mainly follows the CISPR 16-2-1 standard and JJF (military) 27.6-2020 specification. However, traditional calibration methods suffer from problems such as complex equipment, cumbersome operation, and multiple sources of error. For example, the spectrum analyzer method requires multiple devices, including a signal generator, a power divider, and two spectrum analyzers. The calibration process is easily affected by factors such as cable loss and equipment matching, resulting in a total uncertainty of 1.2 dB to 2.5 dB. While the existing network analyzer method requires fewer devices, it is significantly affected by parasitic parameters at high frequencies, and its calibration accuracy needs improvement. Therefore, a current probe calibration scheme that is simple to operate, has low error, and is widely applicable is needed.

[0003] Patent CN107765204A discloses a current probe calibration fixture that solves the problem that traditional calibration fixture structures cannot meet the calibration requirements of ring-shaped closed current probes. It is applicable to current probes of different sizes and has good versatility.

[0004] Patent CN104749544A discloses a method for correcting the temperature error of the transmission impedance of an electromagnetic compatibility current probe. The method calculates the relative error between the transmission impedance of the current probe under different temperature conditions and that under standard temperature conditions, and uses this error to correct the transmission impedance of the electromagnetic probe. Summary of the Invention

[0005] The purpose of this invention is to provide a current probe calibration device and calibration method, which solves the problems of complexity and large error in existing current probe calibration methods.

[0006] To achieve the above objectives, the present invention provides a current probe calibration device, comprising a network analyzer, a calibration fixture, a non-conductive bracket, and an adapter; the calibration fixture is used to simulate cables in actual interference testing; the non-conductive bracket is used to fix the calibration fixture; the input end of the calibration fixture is connected to port PORT1 of the network analyzer, and the output end of the calibration fixture is connected to a load; the current probe to be calibrated is clamped on the center wire of the calibration fixture; the adapter is used to connect the output end of the current probe to be calibrated to port PORT2 of the network analyzer.

[0007] The aforementioned current probe calibration device includes an E5071C network analyzer that supports the 10kHz~8.5GHz frequency band; an adjustable non-conductive bracket; a BNC-N type adapter; and a 50Ω characteristic impedance air coaxial cable with both input and output terminals of the calibration clamp being N-type interfaces.

[0008] This invention also provides a current probe calibration method using the aforementioned current probe calibration device. The method includes the following steps: 1) Network analyzer setup and calibration; setting the frequency range and power level of the network analyzer according to the frequency band to be measured of the current probe to be calibrated, and performing full two-port calibration on the network analyzer to eliminate system errors; 2) Assembling the calibration fixture; 3) Installing the current probe to be calibrated; 4) Starting the network analyzer scan and recording... S 21 5) According to the formula, the amplitude data of the parameters; Z t (dBΩ) = S 21 +34 Calculate the transmission impedance of the current probe to be calibrated to complete the calibration.

[0009] In the above current probe calibration method, step 1) involves performing open-circuit, short-circuit, and load calibrations on the network analyzer to ensure port impedance matching and eliminate system errors.

[0010] The above current probe calibration method, wherein step 2) includes: fixing the calibration fixture horizontally on a non-conductive support, and connecting the input end of the calibration fixture to port PORT1 of the network analyzer, and connecting the output end of the calibration fixture to a load.

[0011] The above current probe calibration method, wherein step 3) includes: clamping the current probe to be calibrated on the center wire of the calibration fixture, closing the latch to ensure that the current probe to be calibrated is tightly closed with an air gap of <0.1mm, and that the magnetic core axis of the current probe to be calibrated is perpendicular to the center wire of the calibration fixture, and connecting the output end of the current probe to be calibrated to port PORT2 of the network analyzer through an adapter.

[0012] In the above current probe calibration method, in step 5), the average value of 10 consecutive measurements is taken as the calibration result.

[0013] Compared with the prior art, the beneficial technical effects of the present invention are: 1) Simplified equipment: Only a few devices such as network analyzers and calibration fixtures are required, reducing connection errors between devices; 2) Improved accuracy: System errors are eliminated through full two-port calibration of the network analyzer, and the total uncertainty is controlled within 2dB, which meets the requirements of CISPR 16-2-1 standard; 3) Improved efficiency: It can automatically switch frequency points, eliminating the need to manually record measurement data from multiple devices, thus improving calibration efficiency by more than 50%; 4) Wide applicability: Within the constant sensing coefficient frequency range of the current probe (e.g., 1MHz~300MHz), the deviation between the measurement results and the typical value of the specification remains within 1dB, making it suitable for calibration of mainstream brand current probes. Attached Figure Description

[0014] The current probe calibration device and calibration method of the present invention are given in the following embodiments and figures.

[0015] Figure 1 This is a block diagram showing the connection for current probe transmission impedance calibration in an embodiment of the present invention. Detailed Implementation

[0016] The following will combine Figure 1 The current probe calibration device and calibration method of the present invention will be described in further detail.

[0017] Figure 1 The diagram shown is a connection block diagram for current probe transmission impedance calibration in an embodiment of the present invention.

[0018] like Figure 1 The current probe calibration device in this embodiment includes a network analyzer, a calibration fixture 1, a non-conductive support, and an adapter; the network analyzer is used to measure... S 21 Parameters (forward transmission coefficient); the calibration fixture 1 is an air coaxial cable with a characteristic impedance of 50Ω, used to simulate the cable in actual interference testing; the non-conductive bracket is used to fix the calibration fixture 1; the adapter is used to connect the output end of the current probe to be calibrated to the port of the network analyzer.

[0019] In this embodiment, the network analyzer is model E5071C, which supports the 10kHz~8.5GHz frequency band; the calibration fixture 1 is a 30cm long 50Ω air coaxial cable, and both ends of the calibration fixture 1 are N-type interfaces; the height of the non-conductive bracket is adjustable; and the adapter is a BNC-N type conversion connector.

[0020] See also Figure 1 This embodiment also provides a current probe calibration method, including the following steps: 1) Network analyzer setup and calibration; Set the frequency range of the network analyzer to the test frequency band (10kHz~500MHz) of the current probe to be calibrated, and the power level to -10dBm; perform open-circuit, short-circuit, and load calibrations on the network analyzer to ensure impedance matching of the network analyzer ports (port PORT1 and port PORT2) and eliminate system errors; 2) Assemble calibration fixture 1; The calibration fixture 1 is horizontally fixed on a non-conductive support, and the input end of the calibration fixture 1 is connected to port PORT1 of the network analyzer, and the output end of the calibration fixture 1 is connected to a 50Ω load. 3) Install the current probe to be calibrated; Clamp the current probe 2 to be calibrated on the center wire of the calibration fixture 1, close the latch to ensure that the current probe 2 to be calibrated is tightly closed (air gap <0.1mm), and the magnetic core axis of the current probe 2 to be calibrated is perpendicular to the center wire of the calibration fixture 1. The output end of the current probe 2 to be calibrated is connected to the port PORT2 of the network analyzer through the adapter. 4) Parameter measurement; Start the network analyzer scan and record. S 21 The amplitude data of the parameters; in this embodiment, the scanning frequency range of the network analyzer is set to 0.3MHz~100MHz; 5) Data conversion; According to the formula Z t (dBΩ) = S 21 +34 Calculate the transmission impedance of the current probe 2 to be calibrated to complete the calibration; in this embodiment, the average value of 10 consecutive measurements is taken as the calibration result.

[0021] This invention provides a calibration method for a current probe within a constant sensing coefficient frequency range. The method utilizes a network analyzer to calibrate the transmission impedance of the current probe. Compared with the spectrum analyzer measurement method, the transmission impedance data obtained by the network analyzer is closer to the typical value of the transmission impedance, and can be better applied to the calibration of current probes in actual engineering applications. Furthermore, the calibration method of this invention simplifies the calibration process, reduces uncertainty, and improves calibration efficiency.

Claims

1. A current probe calibration device, characterized in that, The device includes a network analyzer, a calibration fixture, a non-conductive bracket, and an adapter. The calibration fixture is used to simulate cables in actual interference testing. The non-conductive bracket is used to fix the calibration fixture. The input end of the calibration fixture is connected to port PORT1 of the network analyzer, and the output end of the calibration fixture is connected to a load. The current probe to be calibrated is clamped on the center wire of the calibration fixture. The adapter is used to connect the output end of the current probe to be calibrated to port PORT2 of the network analyzer.

2. The current probe calibration device as described in claim 1, characterized in that, The network analyzer is model E5071C, supporting the 10kHz~8.5GHz frequency band; the non-conductive bracket is height adjustable; and the adapter is a BNC-N type conversion connector.

3. The current probe calibration device as described in claim 1, characterized in that, The calibration fixture is an air coaxial cable with a characteristic impedance of 50Ω, and both the input and output terminals of the calibration fixture are N-type interfaces.

4. A current probe calibration method, characterized in that, The method using the current probe calibration device according to any one of claims 1 to 3 includes the following steps: 1) Network analyzer setup and calibration; Set the frequency range and power level of the network analyzer according to the frequency band to be measured of the current probe to be calibrated, and perform full two-port calibration of the network analyzer to eliminate system errors; 2) Assemble the calibration fixture; 3) Install the current probe to be calibrated; 4) Start the network analyzer scan and record. S 21 The magnitude data of the parameter; 5) According to the formula Z t = S 21 +34 Calculate the transmission impedance of the current probe to be calibrated to complete the calibration.

5. The current probe calibration method as described in claim 4, characterized in that, In step 1), the network analyzer is calibrated with open circuit, short circuit, and load to ensure that the port impedance of the network analyzer is matched and to eliminate system errors.

6. The current probe calibration method as described in claim 4, characterized in that, Step 2) includes: fixing the calibration fixture horizontally on a non-conductive support, with the input end of the calibration fixture connected to port PORT1 of the network analyzer and the output end of the calibration fixture connected to a load.

7. The current probe calibration method as described in claim 4, characterized in that, Step 3) includes: clamping the current probe to be calibrated on the center wire of the calibration fixture, closing the latch to ensure that the current probe to be calibrated is tightly closed with an air gap of <0.1mm, and that the magnetic core axis of the current probe to be calibrated is perpendicular to the center wire of the calibration fixture. The output end of the current probe to be calibrated is connected to port PORT2 of the network analyzer through an adapter.

8. The current probe calibration method as described in claim 4, characterized in that, In step 1), the frequency range of the network analyzer is set to 10kHz~500MHz, and the power level is set to -10dBm; in step 3), the scanning frequency range of the network analyzer is set to 0.3MHz~100MHz.

9. The current probe calibration method as described in claim 4, characterized in that, In step 5), the average value of 10 consecutive measurements is taken as the calibration result.

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