A test method for testing the twist relationship of twisted-pair symmetrical cables using stray capacitance

Abstract

The present invention relates to a testing method for testing the twisting relationship of a twisted symmetrical cable using stray capacitance, and belongs to the field of cable assembly processing. According to the wiring harness in the drawing, the twisted symmetrical cables of the same specification and size are determined and grouped, and the stray capacitance between the pairs of twisted symmetrical cables and the stray capacitance between the twisted symmetrical cables and another group of twisted pairs are tested respectively. Whether the twisted symmetrical relationship is correct is determined according to the test results. The present invention can ensure the correctness of the twisting relationship during the processing process, and avoid the increase of rework time due to unstable data during the debugging process after the processing is completed.

Description

Technical Field

[0001] The invention belongs to the field of cable assembly processing, and in particular relates to a test method for testing the twisting relationship of twisted symmetrical cables by utilizing stray capacitance. Background Art

[0002] Cable assembly products are an indispensable and important part of the signal transmission of an equipment system. In particular, a large number of symmetrical twisted-pair cables are used to ensure the quality of signal transmission. Symmetrical twisted-pair cable assembly products are one of the key components for signal transmission. After processing, the conduction relationship and twisting relationship will directly affect its working performance. In the field of aerospace signal communication, in order to ensure the performance of signal transmission, a large number of twisted-pair cables are used in the cable assemblies supporting its communication. The line pair relationship of cable assemblies is easy to be processed incorrectly during the processing process. At present, there is no better detection method applied in the processing field, which leads to unstable data transmission during the subsequent joint debugging process of general assembly, which increases the difficulty of subsequent joint debugging and troubleshooting. It even causes the problem to pass through layers of barriers, causing the problem to directly enter the hands of users and leave the factory with hidden dangers. Summary of the invention

[0003] The purpose of the present invention is to provide a testing method for testing the twisting relationship of a twisted-pair symmetrical cable using stray capacitance. By testing the stray capacitance between the pairs of twisted-pair symmetrical cables and the stray capacitance between the twisted-pair symmetrical cables and another group of twisted pairs, it is determined whether the twisting relationship of the twisted-pair symmetrical cables is correct, thereby avoiding increased rework time due to unstable data during the debugging process after processing is completed.

[0004] The above-mentioned purpose of the present invention is mainly achieved through the following technical solutions:

[0005] A method for testing the twist relationship of a twisted pair symmetrical cable using stray capacitance comprises the following steps:

[0006] (1) Determine the twisted symmetrical cables and group them according to the wiring harness specifications;

[0007] (2) further grouping the grouped twisted symmetrical cables obtained in step (1) according to the size of the wire bundles, and forming a grouping table;

[0008] (3) Measure the stray capacitance C between the twisted symmetrical cable pairs in the same group obtained in step (2) an The stray capacitance ΔC between the twisted pair cable and the other twisted pair an ;

[0009] (4) Determine the stray capacitance C of each group an Are they approximately equal and much larger than any set of stray capacitance values ​​ΔC? anIf the conditions are met, a qualified judgment result is obtained. If not, an unqualified judgment result is obtained, and the contact parts with incorrect twisting relationships are reworked and confirmed.

[0010] The determination method in step (4) is as follows: an The difference between the two groups is CΔ. Calculate whether CΔ satisfies the requirement of being less than the two adjacent groups of C an and ΔC an Half of the difference; if it meets the requirement, a qualified result is obtained, otherwise an unqualified result is obtained, and the contact parts with incorrect twisting relationship are reworked and confirmed.

[0011] A device for testing the twisted relationship of a twisted symmetrical cable comprises a capacitance measuring module, a control module and a display module. The capacitance measuring module is used to measure the stray capacitance C between the pairs of twisted symmetrical cables. an The stray capacitance ΔC between the twisted-pair cable and the other twisted-pair cable an The measurement results are sent to the control module, which is used to identify and summarize the measurement result data, and determine the twisting relationship of the twisted symmetrical cable, and send the determination results to the display module, which is used to receive the determination results of the control module and display the determination result signal.

[0012] The capacitance measurement module transmits the measurement result to the control module through the 485 communication interface, and the control module sends the determination result to the display module through the serial port.

[0013] Compared with the prior art, the present invention has at least the following beneficial effects:

[0014] (1) The present invention can ensure the correctness of the twisting relationship during the processing process, avoiding the increase of rework time due to unstable data during the debugging process after the processing is completed.

[0015] (2) The present invention preferably inputs the determination method into the control chip to automatically calculate the test results to improve the detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A flow chart of the steps of a testing method for testing the twisting relationship of a twisted pair symmetrical cable using stray capacitance of the present invention;

[0017] Figure 2 A test method for testing the twist relationship of a symmetrical twisted pair cable using stray capacitance according to the present invention is a physical principle diagram of a four-way twisted pair cable;

[0018] Figure 3 A test method for testing the twist relationship of a symmetrical twisted pair cable using stray capacitance according to the present invention is a schematic diagram of a cross-section of a four-way twisted pair cable;

[0019] Figure 4A testing method for testing the twisting relationship of a symmetrical twisted pair cable using stray capacitance of the present invention is a schematic diagram of the twisting relationship of a single-channel twisted pair cable;

[0020] Figure 5 This is a schematic diagram of a device for testing the twisting relationship of a twisted pair symmetrical cable according to the present invention. DETAILED DESCRIPTION

[0021] The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

[0022] like Figure 1 As shown, the method for measuring the twist relationship of a twisted symmetrical cable of the present invention comprises the following steps:

[0023] (1) Determine the twisted symmetrical cables and group them according to the wiring harness specifications;

[0024] (2) further grouping the grouped twisted symmetrical cables obtained in step (1) according to the size of the wire bundles, and forming a grouping table;

[0025] (3) Measure the stray capacitance C between the twisted symmetrical cable pairs respectively. an The stray capacitance ΔC between the twisted-pair cable and the other twisted-pair cable an ;

[0026] (4) Calculate the C of each group obtained in step (3) an Is the error value CΔ between them less than any group C an and any group of ΔC an Half of the difference; if it meets the requirement, a qualified result is obtained, otherwise an unqualified result is obtained, and the contact parts with incorrect twisting relationship are reworked and confirmed.

[0027] like Figure 2 The following is the schematic diagram of a four-way twisted pair cable. Assume that a1 and a2 are twisted pairs and the stray capacitance is C. a1a2 , a3, a4 are a twisted pair, and the stray capacitance is C a3a4 , a5, a6 are a twisted pair, and the stray capacitance is C a5a6 , a7, a8 are a twisted pair, and the stray capacitance is C a7a8 Assume the stray capacitance between the line pairs is ΔC a1a3、 ΔC a1a4、 ΔC a1a5、 ΔC a1a6、 ΔC a1a7、 ΔC a1a8、 ΔC a2a3、 ΔC a2a4、 ΔC a2a5、 ΔC a2a6、 ΔC a2a7、 ΔC a2a8、 ΔCa3a5、 ΔC a3a6、 ΔC a3a7、 ΔC a3a8、 ΔC a4a5、 ΔC a4a6、 ΔC a4a7、 ΔC a4a8、 ΔC a5a7、 ΔC a5a8、 ΔC a6a7、 ΔC a6a8 If there are multiple sets of identical twisted pairs in the same cable assembly and the same connector, the pair stray capacitance is C an , assuming the stray capacitance between the line pairs is ΔC an , n can represent infinite pairs.

[0028] Figure 3 The figure shows the schematic diagram of the cross section of a four-way twisted pair cable. Assume that a1 and a2 are twisted pairs with a relative distance of d. a1a2 , a3, a4 are a twisted pair, the relative distance is d a3a4 , a5, a6 are a twisted pair, the relative distance is d a5a6 , a7, a8 are a twisted pair, the relative distance is d a7a8 If there are multiple sets of identical twisted pairs in the same cable assembly and the same connector, the relative distance between the pairs is d. an , let the relative distance between line pairs be Δd an , n can represent infinite pairs.

[0029] Since the twisted direction and twisted spacing of twisted pair cables of the same specification are consistent, d a1a2 ≈d a3a4 ≈d a5a6 ≈d a7a8 ≈d an , both a1a2 =d a3a4 =d a5a6 =d a7a8 =d an . Let the relative distance between line pairs be Δd a1a3、 Δd a1a4、 Δd a1a5、 Δd a1a6、 Δd a1a7、 Δd a1a8、 Δd a2a3、 Δd a2a4、 Δd a2a5、 Δd a2a6、 Δd a2a7、 Δd a2a8、 Δd a3a5、 Δd a3a6、 Δd a3a7、 Δd a3a8、 Δda4a5、 Δd a4a6、 Δd a4a7、 Δd a4a8、 Δd a5a7、 Δd a5a8、 Δd a6a7、 Δd a6a8 According to the physical characteristics of twisted pair cables, d a1a2 =d a3a4 =d a5a6 =d a7a8 =d an< Δd a1a3、 Δd a1a4、 Δd a1a5、 Δd a1a6、 Δd a1a7、 Δd a1a8、 Δd a2a3、 Δd a2a4、 Δd a2a5、 Δd a2a6、 Δd a2a7、 Δd a2a8、 Δd a3a5、 Δd a3a6、 Δd a3a7、 Δd a3a8、 Δd a4a5、 Δd a4a6、 Δd a4a7、 Δd a4a8、 Δd a5a7、 Δd a5a8、 Δd a6a7、 Δd a6a8、 Δd an .

[0030] Figure 4 The figure shows the schematic diagram of the cross section of a four-way twisted pair cable. Assume that a1 and a2 are a pair of twisted wires, and the relative contact area is S. a1a2 , a3, a4 are a twisted pair, and the relative contact area is S a3a4 , a5, a6 are a twisted pair, and the relative contact area is S a5a6 , a7, a8 are a twisted pair, and the relative contact area is S a7a8 If there are multiple sets of identical twisted pairs in the same cable assembly and the same connector, the relative contact area of ​​the pairs is S. an , let the relative contact area between line pairs be ΔS an , n can represent infinite pairs.

[0031] Since the twisted direction and twisted spacing of twisted pair cables of the same specification are consistent, S is obtained based on the physical properties of the twisted pair cables. a1a2 ≈S a3a4 ≈S a5a6 ≈S a7a8 ≈S an, both S a1a2 =S a3a4 =S a5a6 =S a7a8 =S an . Let the relative contact area between line pairs be ΔS a1a3、 ΔS a1a4、 ΔS a1a5、 ΔS a1a6、 ΔS a1a7、 ΔS a1a8、 ΔS a2a3、 ΔS a2a4、 ΔS a2a5、 ΔS a2a6、 ΔS a2a7、 ΔS a2a8、 ΔS a3a5、 ΔS a3a6、 ΔS a3a7、 ΔS a3a8、 ΔS a4a5、 ΔS a4a6、 ΔS a4a7、 ΔS a4a8、 ΔS a5a7、 ΔS a5a8、 ΔS a6a7、 ΔS a6a8 According to the physical characteristics of twisted pair cables, S a1a2 =S a3a4 =S a5a6 =S a7a8> ΔS a1a3、 ΔS a1a4、 ΔS a1a5、 ΔS a1a6、 ΔS a1a7、 ΔS a1a8、 ΔS a2a3、 ΔS a2a4、 ΔS a2a5、 ΔS a2a6、 ΔS a2a7、 ΔS a2a8、 ΔS a3a5、 ΔS a3a6、 ΔS a3a7、 ΔS a3a8、 ΔS a4a5、 ΔS a4a6、 ΔS a4a7、 ΔS a4a8、 ΔS a5a7、 ΔS a5a8、 ΔS a6a7、 ΔS a6a8 ΔS an .

[0032] A test method for testing the twist relationship of a twisted pair symmetrical cable using stray capacitance. The specific reasoning formula is as follows:

[0033] According to the capacitance calculation formula: C = (∑S) / (4πkd), where ∑ is the dielectric constant of the plate, S is the area of ​​the capacitor plate, d is the distance between the plates, and k is the electrostatic force constant. Therefore, the stray capacitance between the twisted pair is:

[0034] C a1a2 =(∑S a1a2 ) / (4πkd a1a2 ).

[0035] C a3a4 =(∑S a3a4 ) / (4πkd a3a4 ).

[0036] C a5a6 =(∑S a5a6 ) / (4πkd a5a6 ).

[0037] C a7a8 =(∑S a7a8 ) / (4πkd a7a8 ).

[0038] Due to S a1a2 =S a3a4 =S a5a6 =S a7a8 =S an、 d a1a2 =d a3a4 =d a5a6 =d a7a8 =d an After the twisted pair is processed, its physical properties are also fixed, the dielectric constant of the medium of the ∑ plate remains unchanged, and the k electrostatic force constant remains unchanged. Substituting it into the formula, we get: C a1a2 =C a3a4 =C a5a6 =C a7a8 =C an .

[0039] It is further concluded that the stray capacitance between twisted pair wire pairs is:

[0040] ΔC a1a3 =(∑S a1a3 ) / (4πkd a1a3 ), due to S a1a2 >S a1a3 d a1a2< d a1a3 , after substituting into the formula, we can get the stray capacitance value C of the twisted pair a1a2 >Line pair-to-line stray capacitance ΔC a1a3 .

[0041] ΔC a1a4 =(∑Sa1a4 ) / (4πkd a1a4 ), due to S a1a2 >S a1a4 d a1a2< d a1a4 , after substituting into the formula, we can get the stray capacitance value C of the twisted pair a1a2 >Line pair-to-line stray capacitance ΔC a1a4 .

[0042] According to this reasoning, we can finally conclude that: C a1a2 =C a3a4 =C a5a6 =C a7a8 =C an >ΔC a1a3 , ΔC a1a4 , ΔC a1a5 , ΔC a1a6 , ΔC a1a7 , ΔC a1a8 , ΔC a2a3 , ΔC a2a4 , ΔC a2a5 , ΔC a2a6 , ΔC a2a7 , ΔC a2a8 , ΔC a3a5 , ΔC a3a6 , C a3a7 , ΔC a3a8 , ΔC a4a5 , ΔC a4a6 , ΔC a4a7 , ΔC a4a8 , ΔC a5a7 , ΔC a5a8 , ΔC a6a7 , ΔC a6a8 Due to the actual error, the final result is C a1a2 ≈C a3a4 ≈C a5a6 ≈C a7a8 >ΔC a1a3 , ΔC a1a4 , ΔC a1a5 , ΔC a1a6 , ΔC a1a7 , ΔC a1a8 , ΔC a2a3 , ΔC a2a4 , ΔC a2a5 , ΔC a2a6 , ΔC a2a7 , ΔC a2a8 , ΔC a3a5 , ΔC a3a6 , C a3a7 , ΔC a3a8 , ΔC a4a5 , ΔCa4a6 , ΔC a4a7 , ΔC a4a8 , ΔC a5a7 , ΔC a5a8 , ΔC a6a7 , ΔC a6a8 , ΔC an . And C a1a2 ≈C a3a4 ≈C a5a6 ≈C a7a8 ≈C an The error value CΔ between them should also be satisfied. a1a2 -ΔC a1a3 ) / 2, and finally obtain the qualified result.

[0043] like Figure 5 As shown, a schematic diagram of a test device for testing the twisting relationship of a twisted symmetrical cable using stray capacitance; the test device includes a capacitance measurement module, a control module and a display module, the capacitance measurement module is used to measure the stray capacitance Can between the twisted symmetrical cable pairs and the stray capacitance value Can between the twisted symmetrical cable and another group of twisted pairs, and send the measurement results to the control module, the control module is used to identify and summarize the measurement result data, and judge the twisting relationship of the twisted symmetrical cable, and send the judgment result to the display module, the display module is used to receive the judgment result of the control module and display the judgment result signal.

[0044] The capacitance measurement module transmits the measurement result to the control module through the 485 communication interface, and the control module sends the determination result to the display module through the serial port.

[0045] The above description is only the best specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

[0046] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A method for testing the twist relationship of a twisted pair symmetrical cable using stray capacitance, characterized in that: The following steps are involved: (1) Determine the twisted symmetrical cables and group them according to the wiring harness specifications; (2) further grouping the grouped twisted symmetrical cables obtained in step (1) according to the size of the wire bundles, and forming a grouping table; (3) Measure the stray capacitance C between the twisted symmetrical cable pairs in the same group obtained in step (2) an The stray capacitance ΔC between the twisted pair cable and the other twisted pair an ; (4) Determine the stray capacitance C of each group an Are they approximately equal and much larger than any set of stray capacitance values ​​ΔC? an If the conditions are met, a qualified judgment result is obtained. If not, an unqualified judgment result is obtained, and the contact parts with incorrect twisting relationships are reworked and confirmed.

2. A method for testing the twist relationship of a twisted pair symmetrical cable using stray capacitance according to claim 1, characterized in that: The determination method in step (4) is as follows: an The difference between the two groups is CΔ. Calculate whether CΔ satisfies the requirement of being less than the two adjacent groups of C an and ΔC an Half of the difference; if it meets the requirement, a qualified result is obtained, otherwise an unqualified result is obtained, and the contact parts with incorrect twisting relationship are reworked and confirmed.

3. A device for testing the twist relationship of a twisted pair symmetrical cable, characterized in that: The test method according to claim 1 tests the twisting relationship of a twisted pair of symmetrical cables.

4. A device for testing the twist relationship of a twisted pair symmetrical cable according to claim 3, characterized in that: It includes a capacitance measurement module, a control module and a display module. The capacitance measurement module is used to measure the stray capacitance C between the twisted symmetrical cable pairs. an The stray capacitance ΔC between the twisted-pair cable and the other twisted-pair cable an The measurement results are sent to the control module, which is used to identify and summarize the measurement result data, and determine the twisting relationship of the twisted symmetrical cable, and send the determination results to the display module, which is used to receive the determination results of the control module and display the determination result signal.

5. A device for testing the twist relationship of a twisted pair symmetrical cable according to claim 4, characterized in that: The capacitance measurement module transmits the measurement result to the control module through the 485 communication interface, and the control module sends the determination result to the display module through the serial port.

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