CN109541286B - Contact current detection method and tester - Google Patents
Contact current detection method and tester Download PDFInfo
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- CN109541286B CN109541286B CN201811606037.3A CN201811606037A CN109541286B CN 109541286 B CN109541286 B CN 109541286B CN 201811606037 A CN201811606037 A CN 201811606037A CN 109541286 B CN109541286 B CN 109541286B
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- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
Abstract
The invention relates to a tester, in particular to a contact current detection method and a tester, which comprise a sample power supply filtering module, an isolation transformer, a polarity switching module, a sample power supply output socket, a measurement position switching and ground wire breaking module, a measurement network, a switching module for the independent use of the measurement network, a first shielding wire, a second shielding wire, an instrument power supply filtering module, an instrument power supply, an electromagnetic isolation cabin, a signal filter, a universal interface, an oscilloscope module, a sample power supply wire and a metal shielding case. The method and the instrument of the invention optimize the structure of the instrument, and the contact current tester manufactured by using the theories of electromagnetic shielding, filtering and the like is little affected by environmental noise, stable and accurate; the method and the instrument can bear high test input voltage in a short time, and ensure the stability of the instrument; the measuring network is flexible to use and can adapt to the use of samples with different power and environmental requirements.
Description
Technical Field
The invention relates to a tester, in particular to a contact current detection method and a tester.
Background
All electric products can generate human body contact current, and the danger of human body electric shock and death can be caused if the contact current value is too large. Basically, in every electrical appliance safety detection standard, a human body contact current test is carried out, and the condition of the contact current of each part of a sample is required to be measured in the working state of the sample, so that the safety test is a very important safety test. Many product security standards have maintained the test item after undergoing multiple versions of updates, which are expected to persist for a long time in the future.
In the prior art, most laboratories are equipped with a pointer type leakage current meter designed according to the UL standard of the united states, which is produced by the victory corporation of america, deflects the pointer of the meter by means of the lorentz force generated in the pointer coil by the direct current component of the measured current and gives a reading, and obviously, only the contact current average value (direct current) can be measured. At present, electronic products generally adopt a switching power supply, and human body contact current generated by the switching power supply is various non-sinusoidal waveforms, so that a pointer type ammeter cannot accurately measure the human body contact current.
Because the measured human body contact current is usually very low, the safety standard requires that the human body contact current does not exceed a few milliamperes, a signal of the human body contact current is weak, the frequency of the human body contact current is very high, and in addition, electronic products in the surrounding environment comprise laboratory instruments and widely use a switching power supply, particularly a high-power switching power supply used in a laboratory, the human body contact current measured by an oscilloscope is usually accompanied by background noise interference, and the peak amplitude of the human body contact current is difficult to judge or the measurement result is inaccurate.
Due to inadequate understanding of the test by the tester or the complexity of the sample circuit, it can often happen that the contact current measuring network is misconnected on a high-voltage, high-power line such as a mains voltage, which leads to burning of certain components in the contact current measuring network. In view of the ambiguity of the contact current value, numerical inaccuracies resulting from burning out of certain elements in the contact current measurement network are difficult to detect in normal time tests.
At present, no commercialized independent contact current measuring network and a contact current measuring instrument capable of preventing interference exist in the market, and a laboratory basically builds a simple tool and a measuring circuit by an engineer and connects the used circuit and equipment together on a test bed, so that the measuring process is not reliable, all 220V parts are exposed, and great danger is caused in test operation; will be affected by electromagnetic interference and result in inaccurate test results. Therefore, the prior art is in need of improvement and development.
Disclosure of Invention
The present invention is directed to a method and a tester for detecting a contact current, so as to solve the problems of the background art.
In order to achieve the purpose, the invention provides the following technical scheme:
a contact current tester comprises a sample power supply filtering module, an isolation transformer, a polarity switching module, a sample power supply output socket, a measurement position switching and ground wire disconnecting module, a measurement network, a switching module used by the measurement network alone, a first shielding wire, a second shielding wire, an instrument power supply filtering module, an instrument power supply, an electromagnetic isolation cabin, a signal filter, a universal interface, an oscilloscope module, a sample power supply wire and a metal shielding case, wherein the sample power supply filtering module is arranged on the metal case, the power supply wire for supplying power to a sample enters the metal shielding case through the sample power supply filtering module, the sample power supply output socket is arranged on the metal shielding case, the sample power supply filtering module is sequentially connected with the isolation transformer, the polarity switching module and the sample power supply output socket, the sample power supply output socket is connected with a tested sample through the sample power supply wire, the isolation transformer is also respectively connected with a measurement position switching and ground wire disconnecting module and a measurement network independent use switching module, the measurement position switching and ground wire disconnecting module is also respectively connected with a sample power supply output socket and a measurement network, the measurement network is also connected with the measurement network independent use switching module, the measurement network is also connected with a signal filter through a second shielding wire, the signal filter is arranged in front of a universal interface, the universal interface is a BNC connector and is arranged between an electromagnetic isolation cabin and the inside of a metal shielding case, the signal filter is connected with an oscilloscope module through the universal interface, the oscilloscope module is also connected with an instrument power supply filtering module through an instrument power supply, the instrument power supply filtering module is arranged on the metal case, a power line for supplying power to an instrument enters the electromagnetic isolation cabin in the metal shielding case through the instrument power supply filtering module, the measurement position switching and ground wire disconnecting module and the measurement network independent use switching module are A shielding wire; one or more electromagnetic isolation cabins are arranged in the metal shielding case, and devices which can generate electromagnetic interference in normal operation or devices which can cause the conductive continuity of the metal shielding case to be damaged are arranged in the isolation cabins.
As a further scheme of the invention: the sample power supply filtering module is a low-pass filter corresponding to 400Hz, the instrument power supply filtering module is a low-pass filter corresponding to 50Hz, the instrument power supply is a linear variable voltage power supply, the oscilloscope module is an oscilloscope module with a bandwidth of 10MHz, and the metal shielding case is a metal case with conductive continuity.
As a further scheme of the invention: the sample power supply filtering module is a low-pass filter corresponding to 400Hz, the instrument power supply filtering module is a low-pass filter corresponding to 50Hz, the instrument power supply is a linear variable voltage power supply, the oscilloscope module is an oscilloscope module with a bandwidth of 10MHz, and the metal shielding case is a metal case with conductive continuity.
As a further scheme of the invention: the isolation transformer is a 1:1 isolation transformer.
As a further scheme of the invention: the measuring network may comprise 1 or more contact current measuring networks, selected by a combination of switches, only one of which is switched on at a time.
As a further scheme of the invention: the sample power outlet is also disposed within an electromagnetic isolation capsule.
As a further scheme of the invention: the first shielding wire is a double-layer braided aluminum foil shielding wire, and the second shielding wire is a double-layer braided wire.
As a still further scheme of the invention: a detection method of a contact current tester comprises the following steps: the power supply for supplying power to the sample is arranged outside the measuring instrument, after the voltage and the frequency of the power supply are set according to the characteristics of the sample, the L, N power line is connected with the measuring instrument through the sample power supply filtering module and is connected with the sample power line through the sample power supply output socket, so that the power supply is supplied to the sample, the polarity of the sample power supply is switched once through the polarity switching module in the normal state testing process, and the N line is disconnected once or not required to be disconnected in the simulated fault testing process;
the measurement position switching and ground wire disconnecting module keeps the ground wire between the isolation transformer and the sample power output socket connected in the normal state test process, simultaneously keeps the connection between the measurement network and the core wire in the first shielding wire, disconnects the ground wire once according to requirements in the simulated fault test process, and connects the measurement network to the ground wire of the sample power output socket;
the measuring network independently uses the switching module to have 2 working states according to needs, the first one is to use the measuring instrument to supply power to the sample, and the measuring network is connected with the isolation transformer at the moment and is not connected to the shielding layer of the first shielding wire; and the second method is to use the measuring network independently, wherein the power supply and the measuring point which are separated from the tester are respectively the contactable points on the sample, the measuring network is disconnected from the isolation transformer, and the connecting line on the measuring network is switched to the shielding layer of the first shielding line.
As a further scheme of the invention: the measuring network comprises a resistor R1, a resistor RS, a resistor RB, a capacitor CS and a capacitor C1, a measuring terminal A of the measuring network is respectively connected with the resistor RS and the capacitor CS, the other end of the resistor RS is respectively connected with the other end of the capacitor CS, the resistor RB and the resistor R1, the other end of the resistor R1 is connected with the capacitor C1, and the other end of the capacitor C1 is respectively connected with the other end of the resistor RB and a measuring terminal B of the measuring network; the voltage across the resistor RB is set to U1, and the voltage across the capacitor C1 is set to U2.
As a still further scheme of the invention: the oscilloscope module, when in use, will set the type of value displayed according to the type of measurement network selected, set to display the true effective value voltage value when measurement U1 is selected, set to display the peak voltage value when measurement U2 is selected, and set to display the DC voltage value when measuring a DC sample.
Compared with the prior art, the invention has the beneficial effects that: the method and the instrument of the invention optimize the structure of the instrument, and the contact current tester manufactured by using the theories of electromagnetic shielding, filtering and the like is little affected by environmental noise, stable and accurate; the method and the instrument can bear high test input voltage in a short time, and ensure the stability of the instrument; the measuring network is flexible to use and can adapt to the use of samples with different power and environmental requirements.
Drawings
FIG. 1 is a schematic structural diagram of a contact current tester according to the present invention.
Fig. 2 is a schematic circuit diagram of a measuring network in the contact current tester of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-2, in an embodiment of the present invention, a contact current tester includes a sample power supply filter module 1, an isolation transformer 2, a polarity switching module 3, a sample power supply output socket 4, a measurement position switching and ground wire breaking module 5, a measurement network 6, a measurement network independent use switching module 7, a first shielding wire 8, a second shielding wire 9, an instrument power supply filter module 10, an instrument power supply 11, an electromagnetic isolation cabin 12, a signal filter 13, a universal interface 14, an oscilloscope module 15, a sample power line 17, and a metal shielding case 18, where the sample power supply filter module 1 is installed on the metal case 18, a power line for supplying power to a sample enters the metal shielding case 18 through the sample power supply filter module 1, the sample power supply output socket 4 is installed on the metal shielding case 18, and the sample power supply filter module 1 is sequentially connected to the isolation transformer 2, The polarity switching module 3 and the sample power output socket 4, the sample power output socket 4 is connected with a sample 16 to be measured through a sample power line 17, the isolation transformer 2 is also respectively connected with the measurement position switching and ground wire disconnecting module 5 and the measurement network single-use switching module 7, the measurement position switching and ground wire disconnecting module 5 is also respectively connected with the sample power output socket 4 and the measurement network 6, the measurement network 6 is also connected with the measurement network single-use switching module 7, the measurement network 6 is also connected with a signal filter 13 through a second shielding line 9, the signal filter 13 is arranged in front of a universal interface 14, the universal interface 14 is a BNC connector and is arranged between the electromagnetic isolation cabin 12 and the inside of the metal shielding case 18, the signal filter 13 is connected with the oscilloscope module 15 through the universal interface 14, the oscilloscope module 15 is also connected with the instrument power supply filtering module 10 through the instrument power supply, the instrument power supply filtering module 10 is installed on the metal case 18, a power line for supplying power to the instrument enters the electromagnetic isolation cabin 12 in the metal shielding case 18 through the instrument power supply filtering module 10, and the measurement position switching and ground wire disconnecting module 5 and the measurement network single use switching module 7 are both connected to the first shielding wire 8; one or more electromagnetic isolation chambers 12 are arranged in the metal shielding case 18, and devices which can generate electromagnetic interference during normal operation or devices which can cause the conductive continuity of the metal shielding case 18 to be damaged are arranged in the isolation chambers.
In the wire arrangement mode of the conducting wires in the metal shielding case 18, the connecting wires among the sample power supply filtering module 1, the isolation transformer 2, the polarity switching module 3, the sample power supply output socket 4, the measurement position switching and ground wire breaking module 5, the measurement network 6, the measurement network single use switching module 7 and the first shielding wire 8 need to be as short as possible, and are wired in a parallel mutual abutting mode or a twisted pair mode, so that the space area contained between the loops is reduced as much as possible.
The sample power supply filtering module 1 is installed on the metal case 18 and is a low-pass filter corresponding to 400Hz, and a power line for supplying power to a sample enters the metal shielding case 18 through the sample power supply filtering module 1.
The isolation transformer 2 is a 1:1 isolation transformer. Which provides a protection mode for the electric shock injury of people.
The switch in the polarity switching module 3 can realize L, N power line polarity inversion function, and is also responsible for simulating the function of disconnecting the N line in the N line fault test.
The sample power output socket 4 is arranged on the metal shielding case 18, adopts a non-standard universal socket and is responsible for providing test power for samples with plugs of various countries.
The measurement position switching and ground wire disconnecting module 5 is responsible for realizing the function of disconnecting the ground wire between the isolation transformer 2 and the sample power output socket 4 in the test of simulating the disconnection of the ground wire, simultaneously disconnecting the connecting wire between the measurement network 6 and the first shielding wire 8, and connecting the measurement network 6 to the ground wire of the sample power output socket 4.
The measuring network 6 may comprise 1 or more contact current measuring networks, selected by a combination of switches, of which only one is switched on at a time. Outside this core there is a metallic shield can to perform secondary shielding inside the metallic shield can 18. The A end of the measuring network is connected to the measuring position switching and ground wire breaking module 5, the B end is connected to the measuring network single-use switching module 7, and the signal end is connected to the second shielding wire 9.
The measurement network single-use switching module 7 is responsible for independently using the measurement network when the power supply of the tester needs to be separated or the measurement point is two contactable points on the sample, so that the measurement network 6 is disconnected from the isolation transformer 2, and the connecting line on the measurement network 6 is switched to the shielding layer of the first shielding line 8.
The first shield wire 8 is a double-braided aluminum foil shield wire to minimize the space area between the loops and maintain the tightness of the shield layer during the swinging process. Which is responsible for connecting the input of the measurement network to the point on the sample to be measured. The measuring instrument is externally wired with the sample power line 17 in a parallel mutual close mode or a twisted mode, so that the space area contained between loops is reduced as much as possible, and the influence of space electromagnetic radiation is reduced. The tail end of the cable can be provided with a banana plug-in terminal on the core wire and the lead-out wire of the shielding layer, and is provided with a clip which can be used together with the banana plug-in terminal.
The second shielded wire 9 is a double-layer braided wire and is responsible for the connection between the measuring network 6 and the general interface 14, and a signal filter 13 is arranged between the second shielded wire 9 and the general interface 14. The signal filter 13 is a low pass filter corresponding to 1 MHz. The use of shielded wires serves to further reduce the received electromagnetic interference noise.
The instrument power supply filtering module 10 is installed on the metal chassis 18 and is a low-pass filter corresponding to 50Hz, and a power line for supplying power to the instrument enters the electromagnetic isolation cabin 12 in the metal shielding chassis 18 through the instrument power supply filtering module 10.
The instrument power supply 11 is a linear variable voltage power supply, is arranged in the electromagnetic isolation cabin 12, and provides power supply required by normal operation for the oscilloscope module 15.
The electromagnetic isolation chamber 12 is a metal chamber with conductive continuity separately partitioned in the metal shielding cabinet 18, and functions to shield the measurement network 6 and all the connection wires from electromagnetic interference generated by the information processing unit, i.e., the oscilloscope module 15, during operation. Since the oscilloscope module 15 includes a display panel, which needs to have a display window on the chassis during normal operation, this structure will cause the conductive connectivity of the metal-shielded chassis 18 to be damaged, thereby greatly reducing the shielding effectiveness of the metal-shielded chassis 18. Placing the oscilloscope modules 15 in the electromagnetic isolation capsule 12 eliminates this effect while maintaining the shielding effectiveness of the metal shielded enclosure 18.
The signal filter 13 is a low-pass filter corresponding to 1MHz, and is installed in front of the general interface 14, and is responsible for further filtering out electromagnetic interference noise received by the measurement network 6 and all connection wires, so as to provide a purer test signal for the oscilloscope module 15.
The universal interface 14 is a conventional BNC or similar connector mounted between the electromagnetic isolation capsule 12 and the interior of the enclosure. The test signal is provided to the oscilloscope module 15 or an external oscilloscope. In the test method, the oscilloscope module 15 can be used as a display interface of signals and waveforms thereof, and a high-level oscilloscope can be externally connected to be used as the display interface of the signals and the waveforms thereof so as to further analyze and research the measurement signals.
The oscilloscope module 15 is an oscilloscope module having a bandwidth of 10 MHz. It receives the measurement signal after passing through the signal filter 13, and can switch or simultaneously display the peak value, the direct current value and the true effective value voltage value output by the measurement network through the built-in function.
The metallic shield enclosure 18 is a metallic enclosure having conductive continuity that provides rigid support and electromagnetic shielding for internal components, as well as providing some insulation for hazardous voltage components and wires. One or more electromagnetic isolation compartments 12 are provided to contain components that would otherwise cause electromagnetic interference during normal operation, or that would otherwise cause the conductive continuity of the metallic shielded enclosure 18 to be compromised. The metal shielding cabinet 18 may be grounded or not grounded in order to enhance the shielding effect of the electric field.
The detection method of the contact current tester of the present invention is further explained below, and the method includes the steps of: the power supply for supplying power to the sample is arranged outside the measuring instrument, after the voltage and the frequency of the power supply are set according to the characteristics of the sample, the L, N power line is connected with the measuring instrument through the sample power supply filtering module 1 and is connected with the sample power line 17 through the sample power supply output socket 4, so that the power supply is supplied to the sample, the polarity of the sample power supply is switched once through the polarity switching module 3 in the normal state testing process, and the N line is switched off once or not required to be switched off in the simulated fault testing process;
the measurement position switching and ground wire disconnecting module 5 keeps the ground wire between the isolation transformer 2 and the sample power output socket 4 connected in the normal state test process, simultaneously keeps the connection between the measurement network 6 and the core wire in the first shielding wire 8, disconnects the ground wire once according to requirements in the simulation fault test process, and connects the measurement network 6 to the ground wire of the sample power output socket 4;
the measuring network independently uses the switching module 7 to have 2 working states according to the needs, the first is to use the measuring instrument to supply power to the sample, and the measuring network 6 is connected with the isolation transformer 2 at the moment and is not connected to the shielding layer of the first shielding wire 8; the second is to use the measuring network 6 alone, and the power supply and the measuring point which are separated from the tester are respectively the contactable points on the sample, disconnect the measuring network 6 from the isolation transformer 2, and switch the connecting line on the measuring network 6 to the shielding layer of the first shielding line 8.
The measuring network 6 comprises a resistor R1, a resistor RS, a resistor RB, a capacitor CS and a capacitor C1, a measuring terminal A of the measuring network 6 is respectively connected with the resistor RS and the capacitor CS, the other end of the resistor RS is respectively connected with the other end of the capacitor CS, the resistor RB and the resistor R1, the other end of the resistor R1 is connected with the capacitor C1, and the other end of the capacitor C1 is respectively connected with the other end of the resistor RB and a measuring terminal B of the measuring network 6; the voltage across the resistor RB is set to U1, and the voltage across the capacitor C1 is set to U2.
The oscilloscope module 15 will, in use, set the type of value displayed according to the type of measurement network selected, the true effective value voltage value to be displayed when measurement U1 is selected, the peak voltage value to be displayed when measurement U2 is selected, and the dc voltage value to be displayed when measuring a dc sample.
In addition to the shielding, the bus wires, and the first shielding wires 8 used off-board the instrument, it is necessary to reduce the area between the first shielding wires 8 and the sample power wires/connections during the measurement process. The sample power cord 17 is shortened as much as possible and for samples powered using the instrument coupler, a short power cord is prepared by the laboratory.
The solution of the method further provides an extremely economical method for enabling the contact current measuring network 6 to withstand high input voltage and improve device accuracy, see fig. 2 in particular. The target high voltage to prevent overload in this case is an ac voltage of 300V rms. In order to manufacture the overload-proof contact current measuring network, high-voltage-resistant and high-power components are adopted for selecting components of the measuring network, and specific component parameter values and the realization mode are as follows.
1) And the resistor RS adopts a wire-wound power resistor, and the resistor has the characteristics of low inductance parameter and low temperature drift. Two resistors of 3k 20W are used in parallel, and a target resistance value with the accuracy of more than 0.1% can be easily obtained by adopting a parallel processing mode.
2) And the resistor RB adopts a wire-wound power resistor, and the resistor has the characteristics of low inductance parameter and low temperature drift. Two resistors of 1k 10W are used in parallel, and a target resistance value with the accuracy of more than 0.1% can be easily obtained by adopting a parallel processing mode.
3) The capacitor CS is a thin film capacitor having a structure of an extended metal foil, such as CBB capacitor, which has a characteristic of low parasitic inductance. Two capacitors of 0.11uF 400V are used in parallel, a target capacitance value with the precision of more than 0.1% can be easily obtained by adopting a parallel processing mode, and the inductance error can be reduced.
4) The resistor R1 is a metal film resistor, and has the characteristics of low inductance parameter and low temperature drift. Two 20k0.5W resistors are used in parallel, and the target resistance value with the accuracy of more than 0.1% can be easily obtained by adopting a parallel processing mode.
5) Capacitor C1, a thin film capacitor with an extended metal foil structure, such as CBB capacitor, is used, this type of capacitor having low parasitic inductance characteristics. Two capacitors of 0.011uF 200V are used in parallel, a target capacitance value with the precision of more than 0.1 percent can be easily obtained by adopting a parallel processing mode, and the inductance error can be reduced.
The shielding layer of the measuring network 6 in this case uses a thin metal layer, which is wrapped outside the measuring circuit by a conductive continuous structure, so as to shield the electromagnetic radiation in the space. The shielding layer is conductively connected with the B terminal of the measuring circuit.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. Any reference sign in a claim should not be construed as limiting the claim concerned.
Furthermore, it should be understood that although the present description refers to embodiments, not every embodiment may contain only a single embodiment, and such description is for clarity only, and those skilled in the art should integrate the description, and the embodiments may be combined as appropriate to form other embodiments understood by those skilled in the art.
Claims (9)
1. A contact current tester comprises a sample power supply filtering module (1), an isolation transformer (2), a polarity switching module (3), a sample power supply output socket (4), a measurement position switching and ground wire disconnecting module (5), a measurement network (6), a measurement network independent use switching module (7), a first shielding wire (8), a second shielding wire (9), an instrument power supply filtering module (10), an instrument power supply (11), an electromagnetic isolation cabin (12), a signal filter (13), a universal interface (14), an oscilloscope module (15), a sample power line (17) and a metal shielding cabinet (18), wherein the sample power supply filtering module (1) is arranged on the metal cabinet (18), and the power line for supplying power to a sample enters the metal shielding cabinet (18) through the sample power supply filtering module (1), the sample power supply output socket (4) is installed on a metal shielding case (18), the sample power supply filtering module (1) is sequentially connected with an isolation transformer (2), a polarity switching module (3) and the sample power supply output socket (4), the sample power supply output socket (4) is connected with a sample (16) to be measured through a sample power supply line (17), the isolation transformer (2) is further respectively connected with a measurement position switching and ground wire disconnecting module (5) and a measurement network independent use switching module (7), the measurement position switching and ground wire disconnecting module (5) is further respectively connected with the sample power supply output socket (4) and a measurement network (6), the measurement network (6) is further connected with the measurement network independent use switching module (7), the measurement network (6) is further connected with a signal filter (13) through a second shielding line (9), and the signal filter (13) is installed in front of a universal interface (14), the universal interface (14) is a BNC connector and is arranged between the electromagnetic isolation cabin (12) and the interior of the metal shielding case (18), the signal filter (13) is connected with the oscilloscope module (15) through the universal interface (14), the oscilloscope module (15) is also connected with the instrument power supply filtering module (10) through the instrument power supply (11), the instrument power supply filtering module (10) is arranged on the metal case (18), a power line for supplying power to the instrument enters the electromagnetic isolation cabin (12) in the metal shielding case (18) through the instrument power supply filtering module (10), and the measurement position switching and ground line disconnecting module (5) and the measurement network independent use switching module (7) are also connected to the first shielding line (8); one or more electromagnetic isolation chambers (12) are arranged in the metal shielding case (18), and devices which can generate electromagnetic interference in normal operation or devices which can cause the conductive continuity of the metal shielding case (18) to be damaged are arranged in the isolation chambers.
2. The contact current tester according to claim 1, wherein the sample power supply filter module (1) is a low pass filter corresponding to 400Hz, the instrument power supply filter module (10) is a low pass filter corresponding to 50Hz, the instrument power supply (11) is a linear variable voltage power supply, the oscilloscope module (15) is an oscilloscope module having a bandwidth of 10MHz, and the metal shielding cabinet (18) is a metal box having conductive continuity.
3. The contact current tester according to claim 1, wherein the isolation transformer (2) is a 1:1 isolation transformer.
4. Contact current tester according to claim 1, characterized in that the measuring network (6) can contain 1 or more contact current measuring networks, selected by a combination of switches, of which only one is switched on at a time.
5. Contact current tester according to claim 1, characterized in that the sample power outlet socket (4) is also placed in an electromagnetic isolation compartment (12).
6. The contact current tester according to claim 1, wherein the first shielding wire (8) is a double braided wire with aluminum foil and the second shielding wire (9) is a double braided wire.
7. A method of testing using the contact current tester of any one of claims 1-6, comprising the steps of: the power supply for supplying power to the sample is arranged outside the measuring instrument, after the voltage and the frequency of the power supply are set according to the characteristics of the sample, the L, N power line is connected with the measuring instrument through the sample power supply filtering module (1) and is connected with the sample power line (17) through the sample power supply output socket (4), so that the power supply is supplied to the sample, the polarity of the sample power supply is switched once through the polarity switching module (3) in the normal state testing process, and the N line is switched off once or without being switched off according to the requirements in the simulated fault testing process; the measurement position switching and ground wire disconnecting module (5) keeps the ground wire between the isolation transformer (2) and the sample power output socket (4) connected in the normal state test process, simultaneously keeps the connection between the measurement network (6) and the core wire in the first shielding wire (8), disconnects the ground wire once according to requirements in the simulation fault test process, and connects the measurement network (6) to the ground wire of the sample power output socket (4); the measuring network independently uses the switching module (7) to have 2 working states according to needs, the first one is to use the measuring instrument to supply power to the sample, and the measuring network (6) is connected with the isolation transformer (2) at the moment and is not connected to the shielding layer of the first shielding wire (8); and the second method is to use the measuring network (6) independently, wherein the power supply and the measuring point which are separated from the tester are respectively the contactable points on the sample, disconnect the measuring network (6) from the isolation transformer (2), and switch the connecting line on the measuring network (6) to the shielding layer of the first shielding line (8).
8. The detection method of the contact current tester according to claim 7, wherein the measurement network (6) comprises a resistor R1, a resistor RS, a resistor RB, a capacitor CS and a capacitor C1, a measurement terminal A of the measurement network (6) is respectively connected with the resistor RS and the capacitor CS, the other end of the resistor RS is respectively connected with the other end of the capacitor CS, the resistor RB and the resistor R1, the other end of the resistor R1 is connected with the capacitor C1, and the other end of the capacitor C1 is respectively connected with the other end of the resistor RB and the measurement terminal B of the measurement network (6); the voltage across the resistor RB is set to U1, and the voltage across the capacitor C1 is set to U2.
9. The method of claim 8, wherein the oscilloscope module (15) in use will set the type of value displayed according to the type of measurement network selected, set to display true active value voltage value when measurement U1 is selected, set to display peak voltage value when measurement U2 is selected, and set to display dc voltage value when measuring dc samples.
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| CN201811606037.3A CN109541286B (en) | 2018-12-27 | 2018-12-27 | Contact current detection method and tester |
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| CN2165527Y (en) * | 1993-04-21 | 1994-05-18 | 赵遐龄 | Universal safety switch |
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