A method for testing the resistivity of ceramic bundled filament fibers

Abstract

A ceramic bundle fiber resistivity test method belongs to the field of detection technology. Determine the fineness and density of the bundle fiber; after the bundle fiber is impregnated with a resin solution, it is wound onto a winding frame, heated and hardened in an oven, and then pre-cut into a rod-shaped sample; the rod-shaped sample is fixed in a mold to accurately determine the sample length; the cut bundle fiber is fixed to the metal sheet of the test fixture with conductive glue to make the fiber and the metal sheet conductive, and is kept warm in an oven to make the conductive glue fully dry; a high resistance meter is connected to the terminals at both ends of the bundle fiber with a wire, and the resistance value is tested and recorded; the resistivity of the bundle fiber is obtained according to the bundle volume resistivity calculation formula. It can avoid the twisting phenomenon of the bundle fiber during the measurement process and avoid the influence of environmental factors on the fiber resistivity; the embedded bundle fiber is easy to make electrodes, accurately lock the effective conductive length, and realize high-precision resistance testing; and significantly improve the success rate of sample preparation and the efficiency of resistance testing.

Description

Technical Field

[0001] The invention belongs to the field of detection technology, and in particular relates to a method for testing the resistivity of ceramic bundled filament fibers. Background Art

[0002] Ceramic fibers include two categories: non-oxide ceramic fibers and oxide ceramic fibers. Non-oxide ceramic fibers include silicon carbide fibers, silicon nitride fibers, boron nitride fibers, etc. Oxide ceramic fibers include alumina fibers, zirconium oxide fibers, and yttrium aluminum garnet fibers, etc. In addition to common characteristics such as high temperature resistance, low density, and high strength, the above fibers also have different functions and have their own important applications in aerospace and advanced weaponry. One of the important applications is to use the above fibers as dielectric materials to prepare high-performance composite materials for use in electromagnetic functional devices. The resistivity of ceramic fibers is usually used to evaluate their dielectric properties and then their electromagnetic functions. Therefore, how to measure the resistivity of ceramic fibers is an important prerequisite for optimizing the design and preparation of composite materials for electromagnetic properties.

[0003] The national standards GB / T 32993 and GB / T34520.6 specify the volume resistivity test methods for carbon fiber and silicon carbide fiber respectively, which are divided into single fiber resistivity test and bundle resistivity test.

[0004] The single fiber resistivity test is to bond a single fiber to a sample frame with conductive glue to form a reinforcement sheet, and then use a wire to connect the conductive glue and the resistance meter together. By measuring the distance between the conductive glue (the length of the current), the diameter of the single fiber (calculate the current area), and the resistance value after the current is turned on, the resistivity of the fiber is calculated. This method can quickly and easily obtain the test results of the continuous fiber resistivity, but there are also many problems. First, since the volume resistivity of ceramic fibers is generally between 10 4 -10 13 Ω·cm, when using a single fiber test, the fiber diameter is small (about 10μm), and the resistance of a single fiber is often higher than 10 10 Ω, which exceeds the range of conventional resistance meters and requires a high resistance meter. However, the measurement of high resistance is often affected by environmental factors such as electrostatic effects and air humidity, making it difficult to measure accurately. In addition, the current-carrying area calculated using the fiber diameter lacks representativeness, because the diameter of the same fiber may change due to the preparation conditions, and the fiber cross-section is not always a perfect circle, which will cause calculation errors. Finally, the number of single fiber tests is small, the statistics are poor, and it is different from the actual application status.

[0005] On this basis, the applicant disclosed a method for testing the resistivity of ceramic fibers in Chinese patent CN201510061436.6, and made certain improvements to the above-mentioned single fiber testing method. He used double-sided tape to bond multiple ceramic fibers in parallel to a metal plate sample table, and used silver conductive glue to make multiple fibers in parallel; then placed them in a metal electromagnetic shielding box, connected to a high resistance meter, and tested the resistance values ​​corresponding to different numbers of fibers by continuously breaking the fibers, and finally calculated the average volume resistivity. This method can achieve statistical measurement of the resistivity of multiple groups of fibers with different numbers of fibers, improving the test efficiency; and during the test, the samples and sample tables are protected by a metal shielding box, avoiding interference from electromagnetic fields and electrostatic effects during microcurrent measurement, further improving the test accuracy. However, this method still calculates the energized area by measuring the fiber diameter, and the diameter test operation is cumbersome, and the sample number is small, and the statistics are still insufficient.

[0006] In comparison, the fiber volume resistivity is determined by the bundle of fibers by dividing the fiber fineness by the density to calculate the current-carrying area, and then measuring the fiber bundle length and the on-resistance to calculate the volume resistivity of the fiber. The advantage of this method is that the current-carrying area is larger, and the resistance value obtained by the test is relatively small, which can reduce the interference of environmental factors during high-resistance measurement. In addition, since the fiber fineness and density are converted using the precise measurement of mass and length, the calculation of the equivalent current-carrying area is more accurate; and the bundle of fibers data is the statistical result of hundreds of single fibers, which is closer to the actual application state of the fiber, so it is theoretically more reasonable than testing single fibers.

[0007] GB / T 32993 and GB / T34520.6 also specify the bundle resistivity test methods for carbon fiber and silicon carbide fiber, respectively. The cut bundles are fixed between the test electrodes with metal joints, and the fiber volume resistivity is calculated by measuring the electrode spacing, bundle fineness, density and on-resistance. In this process, the fiber and the metal joint are in a rigid mechanical connection, resulting in limited contact area between the fibers and between the fibers and the joint. For low-resistivity carbon fibers, the limited contact area can still achieve conductive connection between different fibers and will not have a significant impact on the measurement results. However, for high-resistivity ceramic fibers, it is impossible to ensure that all fibers are in a conductive state during the conductive process, resulting in large measurement errors. In addition, the bundle fibers are prone to twisting during the sample preparation process, which will also increase the actual energized length and affect the accuracy of the measurement results. It can be seen that the bundle test technology in the existing data is not suitable for high-resistivity ceramic fibers. Summary of the invention

[0008] The purpose of the present invention is to address the above-mentioned deficiencies in the prior art and to provide a ceramic bundle fiber resistivity testing method that can avoid twisting of the bundle during the measurement process and avoid the influence of environmental factors on the fiber resistivity; achieve high-precision resistance testing, improve the success rate of sample preparation, and improve the efficiency of resistance testing.

[0009] The present invention comprises the following steps:

[0010] 1) Determine the fineness and density of the bundled silk fiber (A);

[0011] 2) Preparation of bundled wire samples: After the bundled wire fibers (A) are impregnated with a resin solution, they are wound onto a winding frame, heated and hardened in an oven, and then pre-cut into rod-shaped samples (B);

[0012] 3) Accurately determine the length of the sample: fix the pre-cut rod sample (B) in the mold, and accurately determine the length of the sample to obtain the bundled fiber (C);

[0013] 4) Making electrodes; fixing the bundled fiber (C) on the metal sheet of the test fixture with conductive glue so that the fiber and the metal sheet are conductive, and keeping them warm in an oven to fully dry the conductive glue;

[0014] 5) Test resistance value: Use a wire to connect the megger to the terminals at both ends of the bundled fiber (C), test the resistance value and record it;

[0015] 6) Calculate volume resistivity: The resistivity of the bundle fiber is obtained according to the calculation formula of bundle volume resistivity.

[0016] In step 1), the bundled fiber (A) can be ceramic fiber such as silicon carbide fiber, alumina fiber, etc., with a resistivity of less than 10 10 Ω·cm; the fineness and density can be tested by GB / T 34520.3 (Continuous silicon carbide fiber test method-Part 3: Linear density and density).

[0017] In step 2), the specific method for preparing the bundled wire sample can be: the bundled wire fiber (A) is impregnated with a resin solution under a certain tension, and the resin viscosity is 10 to 100 Pa.s, so that it has a suitable adhesion amount to the bundled wire; the bundled wire impregnated with the resin is wound onto a winding frame, and kept in an oven at 50 to 200°C for 0.5 to 4 hours to fully harden the resin; and the hardened sample is pre-cut to obtain a rod-shaped sample (B).

[0018] The resin can be an insulating resin such as epoxy resin or phenolic resin, and the resistivity is higher than 10 14 Ω·cm;

[0019] The resistivity ratio of the resin to the bundled filament fiber (A) should be greater than 10 4, to ensure that the resin resistance will not affect the bundle fiber resistance during the test.

[0020] The bundled fibers (A) are impregnated with a resin solution to prevent the bundled fibers from twisting during the measurement process and to avoid the influence of environmental factors on the fiber resistivity. The embedded bundled fibers are easy to make electrodes, accurately lock the effective conductive length, and achieve high-precision resistance testing.

[0021] In step 3), the accurate determination of the sample length can fix the pre-cut rod-shaped sample (B) in the mold. When placing the sample, both ends of the sample are extended out of the mold, and the extended parts are quickly cut off by using a cutter to obtain a bundle of fibers (C) with a specific length and a neat cross section. The final sample length is the same as the mold; the mold can be composed of a bottom plate with a groove and an upper cover plate, the groove is used to place the rod-shaped sample (B), and the upper cover plate is used to fix the fiber bundle; the material of the cutter can be high-speed steel or hard alloy. The mold with a groove, upper and lower cover plates is used for sample preparation to improve the success rate of sample preparation.

[0022] In step 4), the specific steps of making the electrode may be: immersing the end of the bundle fiber (C) in conductive glue to ensure that the conductive glue is in full contact with the exposed fiber head in the cut surface, and then using the conductive glue to adhere the sample to the metal sheet of the test fixture, and keeping it in an oven at 50-150°C for 15-60 minutes to allow the conductive glue to be fully dried. At this time, the bundle fiber (C) and the metal sheet are connected through the conductive glue; since only the fibers in the bundle section are exposed, the effective length between the electrodes is the bundle length, which can ensure the consistency and accuracy of the conductive length.

[0023] The conductive adhesive is a silver conductive adhesive with certain adhesiveness and easy to dry, which is convenient for connecting the bundle fiber sample (C) with the metal sheet; the conductive adhesive is used to bond the impregnated bundle fiber to the metal plate. Since only the fibers of the bundle section are exposed, the effective length between the electrodes is the bundle length, thereby ensuring the consistency and accuracy of the conductive length;

[0024] The test fixture can be composed of a terminal, a metal sheet and a bottom plate. The terminal and the metal sheet are made of metals with good conductivity such as copper and aluminum to eliminate the influence of the fixture's own resistance. The test fixture can adhere multiple bundle fibers at the same time to improve the test efficiency, and they will not affect each other during the test. The bottom plate can be made of insulating materials such as bakelite, and the resistivity should be 10 greater than that of the bundle fibers. 4 The above is to avoid the formation of a conductive path during the test; the test fixture is used to test the resistivity, realize the simultaneous testing of multiple bundle wire samples, and significantly improve the test efficiency.

[0025] In step 5), the specific method for testing and recording the resistance value can be: use a wire to connect a high resistance meter to the terminals at both ends of the bundled fiber (C) to form a current path of high resistance meter-terminal-metal sheet-bundled fiber (C)-metal sheet-terminal-high resistance meter, turn on the high resistance meter, and read and record the resistance value after the reading stabilizes; the length of the impregnated bundled fiber after cutting is used as the actual energized length; since the resistivity of some ceramic fibers changes with temperature, the test should be carried out at room temperature, and the test voltage should be lower than 50V to avoid high voltage and high current causing the fiber to heat up sharply, resulting in resistivity test errors; in addition, the humidity should be lower than 55% to avoid water vapor film formation affecting the measurement results.

[0026] In step 6), the specific method for calculating the volume resistivity can be: using the bundle volume resistivity calculation formula S=RT / Lρ, calculate the resistivity of multiple bundle fibers (C) to find the average volume resistivity of the fibers; wherein R represents the resistance of the fiber bundle, T represents the fineness of the fiber bundle, L represents the length of the fiber bundle, and ρ represents the density of the fiber bundle.

[0027] The invention calculates the volume resistivity of a plurality of bundle fibers by using the fineness, density, length and conduction resistance of the bundle fibers, thereby realizing accurate measurement of the fiber resistivity.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention utilizes insulating resin to impregnate ceramic bundle fibers, which can prevent the bundle fibers from twisting during the measurement process, thereby accurately limiting the length of the sample.

[0030] 2. After resin impregnation and curing, it can protect the ceramic fiber and prevent the influence of environmental factors such as static electricity, humidity, etc. on the fiber resistivity during high resistance testing;

[0031] 3. The embedded wire bundle is easy to make electrodes. The fiber contacts the conductive glue only at the cross section of the wire bundle, which can accurately lock the effective conductive length and achieve high-precision resistance testing;

[0032] 4. Use the independently designed mold with grooves, upper and lower covers to make samples, which significantly improves the success rate of sample making;

[0033] 5. The self-designed resistivity test fixture is used to test multiple bundled wire samples simultaneously, which significantly improves the efficiency of resistance testing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of the wire bundle dipping process.

[0035] Figure 2 This is a schematic diagram of the structure of the bundled fiber sample preparation mold.

[0036] Figure 3 This is a schematic diagram of the resistance test fixture. DETAILED DESCRIPTION

[0037] The present invention will be further described below in conjunction with examples. The examples are only used to further illustrate the content of the invention and are not intended to limit the content of the invention.

[0038] The embodiment of the present invention includes the following steps:

[0039] Step 1, determining the fineness and density of the bundled filament fiber (A); wherein the fineness and density are tested according to GB / T 34520.3 (Continuous silicon carbide fiber test method - Part 3: Linear density and density).

[0040] Step 2, prepare the bundle sample; soak the bundle fiber (A) with resin solution under a certain tension, the resin viscosity is 10-100Pa.s, so that it has a suitable amount of adhesion to the bundle. Wind the bundle fiber soaked with resin onto the winding frame, keep it in an oven at 50-200℃ for 0.5-4h to fully harden the resin; then pre-cut the hardened sample to obtain a rod sample (B); the rod sample (B) is slightly longer than the length of the homemade mold.

[0041] The bundled fiber (A) is a ceramic fiber such as silicon carbide fiber and alumina fiber (with a resistivity of less than 10 10 Ω·cm), the resin is an insulating resin such as epoxy resin or phenolic resin (resistivity higher than 10 14 Ω·cm). The resistivity ratio of resin to fiber should be greater than 10 4 , to ensure that the resin resistance will not affect the bundle fiber resistance during the test.

[0042] Step 3: Accurately determine the length of the sample; fix the sample in the mold and place it so that both ends of the bundled fiber sample extend out of the mold. Use a cutter to quickly cut off the extended parts to obtain a bundled fiber (C) of a specific length and a neat cross section. The final sample length is the same as the mold. The mold consists of a bottom plate with a groove and an upper cover plate. The groove is used to place the pre-cut sample (B), and the upper cover plate is used to fix the fiber bundle.

[0043] Step 4, making electrodes; immersing the end of the bundled fiber (C) in conductive glue, ensuring that the conductive glue is in full contact with the exposed fiber head in the cut surface, and then using the conductive glue to adhere the sample to the metal sheet of the test fixture, and then keeping it in an oven at 50-150°C for 15-60 minutes to allow the conductive glue to fully dry. At this time, the bundled fiber (C) and the metal sheet are connected through the conductive glue.

[0044] The conductive glue is a silver conductive glue with certain adhesion and easy drying, which is convenient for connecting the bundled fiber sample (C) with the metal sheet. The test fixture is composed of a terminal, a metal sheet and a bottom plate. The terminal and the metal sheet are made of metals with good conductivity such as copper and aluminum to eliminate the influence of the fixture's own resistance; the bottom plate is made of insulating materials such as bakelite, and the resistivity should be 10 greater than that of the bundled fiber. 4 Above, avoid forming a conductive path during the test.

[0045] Step 5, test the resistance; use wires to connect the high resistance meter to the terminals at both ends of the bundled fiber (C) to form a current path of high resistance meter-terminal-metal sheet-bundled fiber (C)-metal sheet-terminal-high resistance meter, turn on the high resistance meter, read and record the resistance value after the reading stabilizes.

[0046] Since the resistivity of some ceramic fibers changes with temperature, the test should be carried out at room temperature and the test voltage should be lower than 50V to avoid high voltage and high current causing the fiber to heat up sharply and cause resistivity test errors; in addition, the humidity should be lower than 55% to avoid water vapor film formation affecting the measurement results.

[0047] Step 6, calculate the volume resistivity; use the bundle volume resistivity calculation formula S = RT / Lρ (R represents the resistance of the fiber bundle, T represents the fineness of the fiber bundle, L represents the length of the fiber bundle, and ρ represents the density of the fiber bundle) to calculate the resistivity of multiple bundle fibers (C) and find the average volume resistivity of the fibers.

[0048] Specific examples are given below.

[0049] Example 1: Testing the resistivity of continuous silicon carbide fibers

[0050] Material: Continuous Silicon Carbide Fiber

[0051] Epoxy resin glue: Araldite Standard, specific gravity about 1.05

[0052] Conductive glue: SPI silver conductive paint

[0053] Cutter: Carbide blade

[0054] Instruments and equipment: High resistance meter: Keithley-6517B

[0055] Sample making mold: self-made according to needs

[0056] Test fixture: self-made as needed

[0057] Testing process:

[0058] Step 1: Test and obtain the fineness of silicon carbide bundled filaments to be 180Tex and the density to be 3.1g / cm 3 .

[0059] Step 2: Use a wire sample preparation device (such as Figure 1 As shown), the bundled wire fibers on the winding tube 1 are infiltrated in an impregnation tank 2 filled with a resin solution with a viscosity of 45 Pa.s through a roller 3; the bundled wire impregnated with the resin solution is wound onto a winding frame 4, and heated and hardened in an oven at 150°C for 2 hours; then, bundled wire samples with a length of about 11 cm are pre-cut for use.

[0060] Step 3, a self-made sample preparation mold, the sample preparation mold can be composed of a bottom plate 9 with a groove and an upper cover plate 6, the groove is used to place the rod-shaped sample (B), and the upper cover plate 6 is used to fix the fiber bundles; the groove can be a V-shaped groove 10; in this embodiment, 5 bundles of fiber samples 5 (rod-shaped samples (B)) are placed in the sample preparation mold (such as Figure 2 At least four corresponding screw holes 8 are provided on the bottom plate 9 and the upper cover plate 6. The upper cover plate 6 and the bottom plate 9 are fixedly connected by tightening screws 7 to fix the bundled wire sample 5 in the V-shaped groove 10. The parts of the bundled wire sample 5 extending out of the mold are quickly cut off by a cutter to obtain a bundled wire fiber sample 15 with a length of 10 cm and a neat fracture.

[0061] Step 4: Self-made test fixture, the test fixture is composed of a terminal 11, a metal sheet 12 and an insulating base plate 13. A plurality of metal sheets 12 are arranged on the insulating base plate 13. Five cut bundled fiber samples 15 are fixed on the test fixture (such as Figure 3 After the five samples are fixed, the entire fixture is kept in an oven at 60°C for 1h to fully dry the conductive adhesive; in this embodiment, the metal sheet 12 is made of copper.

[0062] Step 5. Use a dehumidifier to control the test environment humidity to 40%. Use a wire to connect the Keithley-6517B high resistance meter to the two terminal posts of one group of bundled fibers. Turn on the high resistance meter, set the voltage to 30V, wait for 30 seconds after starting the measurement, and read the resistance value of 0.3636MΩ after the reading stabilizes. Then disconnect the power supply, connect the high resistance meter to the other 4 groups of terminals, and repeat the above operation.

[0063] Step 6: According to the fiber fineness of the bundled yarn is 180Tex and the density is 3.1g / cm 3 , length and resistance measurement values, the resistivity values ​​of 5 groups of bundled fibers were calculated, and finally the average resistivity value of the fiber was found to be 21.11Ω·cm.

[0064] The present invention can realize the rapid and accurate measurement of the resistivity of ceramic fibers. The present invention soaks the bundled fibers with resin under stress, and then heats and hardens them to form fiber rods; then cuts them into multiple bundled fiber samples with specific lengths and neat cross-sections on a sample preparation mold; then wraps the ends of the bundled fibers with conductive glue, and bonds them to the metal sheet of the test fixture to make the fibers conductive to the metal plate; after the conductive glue is fully dried, the resistance values ​​of the multiple bundled fibers are measured with a high resistance meter; finally, the volume resistivity of the multiple bundled fibers is calculated based on the fineness, density, energized length and test resistance of the bundled fibers, and the average value is calculated. The present invention provides a simple and feasible method for accurately measuring the resistivity of ceramic fibers.

Claims

1. A method for testing the resistivity of ceramic bundled filament fibers, characterized in that The following steps are involved: 1) Determine the fineness and density of the bundled fiber A; 2) Preparation of bundled wire samples: After the bundled wire fiber A is impregnated with the resin solution, it is wound onto a winding frame, heated and hardened in an oven, and then pre-cut into rod-shaped samples B; 3) Determine the sample length: fix the pre-cut rod sample B in the mold, and determine the sample length to obtain the bundle fiber C; 4) Make electrodes; fix the bundled fiber C on the metal sheet of the test fixture with conductive glue to make the fiber and the metal sheet conductive, and keep them warm in an oven to make the conductive glue fully dry; The specific steps of making the electrode are: immersing the end of the bundle fiber C in the conductive glue, ensuring that the conductive glue is in full contact with the exposed fiber head in the cut surface, and then using the conductive glue to adhere the sample to the metal sheet of the test fixture, and keeping it in an oven at 50-150° C. for 15-60 minutes to fully dry the conductive glue, at which time the bundle fiber C and the metal sheet are connected through the conductive glue; since only the fibers in the bundle section are exposed, the effective length between the electrodes is the bundle length; 5) Test resistance value: Use a wire to connect the megger to the terminals at both ends of the bundle fiber C, test the resistance value and record it; The specific method of testing and recording the resistance value is as follows: connect the high resistance meter to the terminals at both ends of the bundled silk fiber C with a wire to form a current path of high resistance meter-terminal-metal sheet-bundled silk fiber C-metal sheet-terminal-high resistance meter, turn on the high resistance meter, read the resistance value after the reading is stable and record it; take the length of the impregnated bundled silk fiber after cutting as the actual energized length; 6) Calculate volume resistivity: The resistivity of the bundle fiber is obtained according to the calculation formula of bundle volume resistivity; The specific method for calculating the volume resistivity is: using the bundle volume resistivity calculation formula S = RT / Lρ, calculating the resistivity of multiple bundle fibers C, and finding the average volume resistivity of the fibers; wherein R represents the resistance of the fiber bundle, T represents the fineness of the fiber bundle, L represents the length of the fiber bundle, and ρ represents the density of the fiber bundle.

2. A ceramic bundle fiber resistivity testing method as claimed in claim 1, characterized in that In step 1), the bundle fiber A is made of silicon carbide fiber and alumina fiber, and the resistivity is less than 10 10 Ω·cm.

3. A ceramic bundle fiber resistivity testing method as claimed in claim 1, characterized in that In step 2), the bundled fibers A are soaked with a resin solution to prevent the bundled fibers from twisting during the measurement process and to prevent environmental factors from affecting the fiber resistivity. The embedded bundled fibers are easy to make electrodes, lock the effective conductive length, and realize resistance testing.

4. A ceramic bundle fiber resistivity testing method as claimed in claim 1, characterized in that In step 2), the resin is epoxy resin or phenolic resin, and the resistivity is higher than 10 14 Ω·cm; the resistivity ratio of the resin to the bundled fiber A is greater than 10 4 .

5. A ceramic bundle fiber resistivity testing method as claimed in claim 1, characterized in that In step 3), the sample length is determined by fixing the pre-cut rod-shaped sample B in a mold, placing the sample so that both ends extend out of the mold, and using a cutter to quickly cut off the extended parts to obtain a bundle of fibers C with a specific length and a neat cross-section. The final sample length is the same as the mold; the mold is composed of a bottom plate with a groove and an upper cover plate, the groove is used to place the rod-shaped sample B, and the upper cover plate is used to fix the fiber bundle; the sample is prepared using a mold with a groove, an upper cover plate, and a lower cover plate.

6. A ceramic bundle fiber resistivity testing method as claimed in claim 5, characterized in that The cutter is made of high speed steel or hard alloy.

7. A ceramic bundle fiber resistivity testing method as claimed in claim 1, characterized in that In step 4), the test fixture is composed of a terminal, a metal sheet and a bottom plate, and the terminal and the metal sheet are made of copper or aluminum metal with good conductivity to eliminate the influence of the fixture's own resistance; The bottom plate is made of insulating material, and the resistivity should be 10 greater than that of the bundled fiber 4 The above is to avoid the formation of a conductive path during the test; when the test fixture is used to test the resistivity, multiple bundled wire samples can be tested simultaneously.

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