Anti-alternating magnetic field interference circuit of voltage sampling loop and standard electric energy meter thereof

Abstract

The utility model relates to the technical field of standard electric energy meters, in particular to an anti-alternating magnetic field interference circuit of a voltage sampling loop and a standard electric energy meter thereof, the circuit comprises an input end and an output end, the positive electrode of the input end is signal input, the positive electrode of the output end is signal output, and the negative electrodes of the input end and the output end are grounded; n is a positive integer larger than or equal to 2, the 2N plug-in resistors are symmetrically arranged and connected to the target circuit board, the first plug-in resistor is connected with the other side of the input end, the 2Nth plug-in resistor is connected with the other side of the output end, the 2N plug-in resistors are connected through cross routing, 2M loops are formed, and M is a positive integer. Therefore, the problems that although the area of a loop is reduced as much as possible in an existing standard electric energy meter voltage sampling loop layout, a certain single loop area still exists, induced voltage is generated in a circuit, and the accuracy of voltage sampling is affected are solved.

Description

Technical Field

[0001] The utility model relates to the technical field of standard electric energy meters, and particularly relates to an anti-alternating magnetic field interference circuit for a voltage sampling circuit and a standard electric energy meter thereof. Background Art

[0002] As a high-precision electric energy metering device, 0.01-level standard electric energy meter products are widely used in fields such as electric energy metering calibration, laboratory metering benchmarks, power quality monitoring, and power system testing to ensure the accuracy and reliability of the power system. The standard meter mainly consists of key module circuits such as a voltage sampling circuit, a current sampling circuit, and an ADC sampling circuit.

[0003] As Figure 1 shown, the voltage sampling circuit of the standard electric energy meter generally adopts the resistance voltage division method to convert the measured voltage into a corresponding measured voltage signal and input it into the electric energy meter. In the resistance voltage division circuit, multiple resistors are connected in series to form a voltage divider. When the power supply voltage V IN passes through multiple series-connected resistors, according to Ohm's law, the relationship between the voltage drop V on the resistor, the resistance value R of the resistor, and the current I passing through the resistor is:

[0004] V = IR

[0005] As Figure 1 shown, R1-R5 are upper voltage division resistors, and R6 is a lower voltage division resistor. The voltage division ratio of the resistor is determined by the resistance values of each resistor:

[0006]

[0007] The resistance voltage division circuit is usually used for precise voltage measurement. High-precision resistors with high temperature stability and long-term stability are often selected to provide a more accurate voltage division ratio and ensure the accuracy of the output voltage.

[0008] It can be seen from this that the precision level of the resistor in this method is directly related to the accuracy of the measurement, and there are high requirements for the precision and stability of the sampling resistor. Therefore, the drift of the resistor value will directly affect the test result. Although the high-precision chip resistor can reach a stability index of 0.001%, its long-term stability is insufficient, which may lead to the deterioration of the overall technical indicators of the standard meter.

[0009] To solve this problem, more precise metal foil resistors are often selected in practical applications. Metal foil resistors are usually designed with a larger package size and are installed in an insertion manner to ensure higher precision and stability. Specifically, as Figure 2As shown in the figure, the metal foil resistor is made by vacuum melting to form nickel-chromium alloy, and then the metal foil is made by rolling. Then the metal foil is bonded to the alumina ceramic substrate, and the shape of the metal foil is controlled by photolithography technology to control the resistance. The metal foil resistor is currently the resistor with the best controllable performance. The chip of the metal foil resistor is sealed in a metal shell, so that the resistor chip is not easily affected by the external environment during operation. However, compared with surface-mounted precision resistors, the metal foil resistor has a larger package size and is an insertion component. The resistor body and the peripheral circuit together form a closed circuit, increasing the loop area. Inside the electric energy meter, there are magnetic field interferences generated by the current channel and other continuously changing external magnetic field interferences. When the alternating magnetic field passes through the loop, induced electromotive forces of different magnitudes and directions will be formed. The induced current is superimposed on the circuit, affecting the accuracy of the output voltage.

[0010] The induced voltage generated by the alternating magnetic field in this closed loop can be obtained according to the law of electromagnetic induction:

[0011]

[0012] φ B =B(t)×A×cos(θ)(2)

[0013] B(t)=B max ×sin(ωt)(3)

[0014] Among them, V RMS is the effective value of the induced voltage, V max is the maximum induced voltage, N is the number of turns of the coil, Φ B is the magnetic flux, t is the time, B(t) is the magnetic field strength of the alternating magnetic field, A is the loop area, θ is the angle between the magnetic field direction and the loop normal direction, B max is the maximum value of the magnetic field strength, and ω is the angular frequency.

[0015] It can be seen from the formula that the current loop area A is proportional to the induced voltage generated by the circuit.

[0016] It can be seen from this that although the metal foil resistor can reduce the problem of the influence of the space magnetic field by the method of space magnetic field shielding, this method requires that the shielding material has high magnetic permeability and sufficient thickness, and the implementation difficulty is great.

[0017] Furthermore, as Figure 3 shown, the circuit layout of the resistor voltage division circuit only considers reducing the loop area of the circuit. However, due to the large package size of the insertion resistor and the fact that the input is a strong electrical signal, considering the problems of leakage of the strong voltage between the boards and the interference of the electric field, a certain safety distance needs to be ensured, and there will inevitably be a certain loop area in the circuit.

[0018] The circuit layout area A in the figure is 200 mm 2 , assuming that there is an alternating magnetic field perpendicular to the loop plane around the circuit, with a magnetic field intensity B(t) of 0.2 mT and a magnetic field frequency of 50 Hz, substituting into formulas (1)-(3), calculate the effective value V of the induced voltage generated in the loop RMS is approximately 8.9 μV. The alternating magnetic field generates an induced voltage, resulting in an induced current superimposed in the circuit, directly affecting the output voltage across the voltage-dividing resistor R6 and reducing the measurement accuracy. Summary of the Invention

[0019] The present invention provides an anti-alternating magnetic field interference circuit for a voltage sampling circuit and a standard watt-hour meter, to solve the problems that although the layout of the voltage sampling circuit of the existing standard watt-hour meter minimizes the area of the loop as much as possible, there is still a certain single-loop area, resulting in the generation of an induced voltage in the circuit and affecting the accuracy of voltage sampling.

[0020] The first aspect of the present invention provides an anti-alternating magnetic field interference circuit for a voltage sampling circuit and a standard watt-hour meter, including: an input end and an output end, the positive pole of the input end is for signal input, the positive pole of the output end is for signal output, and the negative poles of the input end and the output end are both grounded; 2N plug-in resistors, where N is a positive integer greater than or equal to 2, the 2N plug-in resistors are symmetrically placed, the first plug-in resistor is connected to the other side of the input end, the 2Nth plug-in resistor is connected to the other side of the output end, and the 2N plug-in resistors are connected in series by cross-wiring, forming 2M loops, where M is a positive integer.

[0021] Optionally, the 2N plug-in resistors are connected to a target circuit board, and the target circuit board is perpendicular to the alternating magnetic field.

[0022] Optionally, each plug-in resistor has the same specification.

[0023] Optionally, the current directions of each loop are opposite, and the loop areas of each loop tend to be the same.

[0024] Optionally, the symmetric plug-in resistors in each loop respectively form a first induced electromotive force and a second induced electromotive force, and the direction of the first induced electromotive force is opposite to the direction of the second induced electromotive force, and the induced voltage values of the first induced electromotive force and the second induced electromotive force are the same.

[0025] The second aspect of the present invention provides a standard watt-hour meter, and the standard watt-hour meter adopts the anti-alternating magnetic field interference circuit for the voltage sampling circuit described above.

[0026] The anti-alternating magnetic field interference circuit of the voltage sampling circuit and the standard watt-hour meter proposed in the present utility model, compared with the traditional electromagnetic shielding method using high-permeability materials for multi-layer shielding, optimizes the layout based on the existing voltage sampling circuit for the precision components and circuits of the voltage sampling circuit of a 0.01-class standard watt-hour meter from the influences of the alternating magnetic field on the circuit in the horizontal and vertical directions, thereby reducing the interference of the alternating magnetic field on the circuit in multiple dimensions, ensuring the accuracy of the voltage sampling signal, with low cost and being easy to implement.

[0027] Additional aspects and advantages of the present utility model will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present utility model. Description of the Drawings

[0028] The above-mentioned and / or additional aspects and advantages of the present utility model will become apparent and easy to understand from the following description of the embodiments in conjunction with the drawings, where:

[0029] Figure 1 Schematic diagram of the existing voltage sampling circuit using the resistor voltage division method;

[0030] Figure 2 Schematic diagram of the metal foil resistor;

[0031] Figure 3 Schematic diagram of the circuit layout of the existing voltage sampling circuit, where J1 is the signal input terminal, J2 is the signal output terminal, R1-R5 are the upper voltage division resistors, and R6 is the lower voltage division resistor;

[0032] Figure 4 Schematic diagram of an anti-alternating magnetic field interference circuit for a voltage sampling circuit provided by the present utility model;

[0033] Figure 5 Schematic diagram of an anti-alternating magnetic field interference circuit for a voltage sampling circuit provided by the present utility model when 6 metal foil resistors are selected;

[0034] Figure 6 Schematic diagram of an anti-alternating magnetic field interference circuit for a voltage sampling circuit provided by the present utility model when 8 metal foil resistors are selected.

[0035] Explanation of the reference numerals in the drawings:

[0036] 40 - Anti-alternating magnetic field interference circuit of the voltage sampling circuit, 401 - Input terminal, 402 - Output terminal, and 403 - 2N plug-in resistors. Detailed Embodiment

[0037] Embodiments of the present utility model will be described in detail below. Examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present utility model, and should not be construed as a limitation of the present utility model.

[0038] The anti-alternating magnetic field interference circuit of the voltage sampling circuit and its standard watt-hour meter of the present utility model will be described below with reference to the accompanying drawings. Aiming at the problem that the existing voltage sampling circuit of the standard watt-hour meter mentioned in the above background technology will not only generate electromagnetic interference that interferes with itself and other devices during operation, but also be affected by the spatial electromagnetic field, thereby reducing the accuracy of voltage measurement, this embodiment provides an anti-alternating magnetic field interference circuit for the voltage sampling circuit. In this circuit, on the basis of the existing voltage sampling circuit, the precision devices and lines of the voltage sampling circuit of the 0.01-level standard watt-hour meter are reasonably arranged to weaken the interference of the power frequency magnetic field on the circuit and ensure the accuracy of the voltage sampling signal.

[0039] Specifically, Figure 4 It is a schematic diagram of an anti-alternating magnetic field interference circuit for a voltage sampling circuit provided by the present utility model.

[0040] As Figure 4 shown, the anti-alternating magnetic field interference circuit 40 of the voltage sampling circuit includes: an input terminal 401, an output terminal 402, and 2N plug-in resistors 403, where N is a positive integer greater than or equal to 2.

[0041] Among them, the positive pole of the input terminal 401 is for signal input, and the negative pole of the input terminal 401 is grounded. The positive pole of the output terminal 402 is for signal output, and the negative pole of the output terminal 402 is grounded. The 2N plug-in resistors 403 are symmetrically arranged and connected on the target circuit board, and the target circuit board is perpendicular to the alternating magnetic field. The first plug-in resistor is connected to the other side of the input terminal 401, the 2Nth plug-in resistor 403 is connected to the other side of the output terminal 402, and the 2N plug-in resistors 403 are connected in series by cross-wiring, forming 2M loops, where M is a positive integer.

[0042] For example, as Figure 5As shown, when N = 3, the anti-alternating magnetic field interference circuit of the voltage sampling circuit includes a first metal foil resistor R1, a second metal foil resistor R2, a third metal foil resistor R3, a fourth metal foil resistor R4, a fifth metal foil resistor R5, and a sixth metal foil resistor R6. The 6 plug-in resistors 403 are symmetrically arranged on the target circuit board perpendicular to the alternating magnetic field. The negative terminal of the first metal foil resistor R1 is connected to the other side of the input terminal 401. The positive terminal of the first metal foil resistor R1 is connected to the negative terminal of the second metal foil resistor R2. The positive terminal of the second metal foil resistor R2 is connected to the negative terminal of the third metal foil resistor R3. The positive terminal of the third metal foil resistor R3 is connected to the positive terminal of the fourth metal foil resistor R4. The negative terminal of the fourth metal foil resistor R4 is connected to the positive terminal of the fifth metal foil resistor R5. The negative terminal of the fifth metal foil resistor R5 is connected to the positive terminal of the sixth metal foil resistor R6. The sixth metal foil resistor R6 is connected to the other side of the output terminal 402, thus forming two loops A1 and A2.

[0043] As Figure 6 shown, when N = 4, the anti-alternating magnetic field interference circuit of the voltage sampling circuit includes a first metal foil resistor R1, a second metal foil resistor R2, a third metal foil resistor R3, a fourth metal foil resistor R4, a fifth metal foil resistor R5, a sixth metal foil resistor R6, a seventh metal foil resistor R7, and an eighth metal foil resistor R8. The 8 plug-in resistors 403 are symmetrically arranged on the target circuit board perpendicular to the alternating magnetic field. The negative terminal of the first metal foil resistor R1 is connected to the other side of the input terminal 401. The positive terminal of the first metal foil resistor R1 is connected to the negative terminal of the second metal foil resistor R2. The positive terminal of the second metal foil resistor R2 is connected to the negative terminal of the third metal foil resistor R3. The positive terminal of the third metal foil resistor R3 is connected to the negative terminal of the fourth metal foil resistor R4. The positive terminal of the fourth metal foil resistor R4 is connected to the positive terminal of the fifth metal foil resistor R5. The negative terminal of the fifth metal foil resistor R5 is connected to the positive terminal of the sixth metal foil resistor R6. The negative terminal of the sixth metal foil resistor R6 is connected to the positive terminal of the seventh metal foil resistor R7. The negative terminal of the seventh metal foil resistor R7 is connected to the positive terminal of the eighth metal foil resistor R8. The negative terminal of the eighth metal foil resistor R8 is connected to the other side of the output terminal 402, thus forming 4 loops A1, A2, A3, and A4.

[0044] In some embodiments, the specifications of each plug-in resistor are the same.

[0045] Specifically, since the specifications of each plug-in resistor are the same, the 2N plug-in resistors 403 can be placed randomly as long as they are arranged symmetrically.

[0046] In some embodiments, the current directions of each loop are opposite, and the loop areas of each loop tend to be the same.

[0047] Specifically, asFigure 5 As shown, taking N = 3 as an example, in the circuit with cross-wired traces, since the induced signals generated in the loops with opposite currents will cancel each other out, it is necessary to ensure that the area enclosed by the input lines is as equal as possible to the area enclosed by the output lines, and the number of loops formed in the circuit is preferably even, so that under the action of external electromagnetic interference, the interference generated inside the lines can neutralize each other, reducing the interference of the alternating magnetic field on the loop area in the plane direction of the circuit board.

[0048] In some embodiments, the symmetrically mounted resistors in each loop respectively form a first induced electromotive force and a second induced electromotive force, and the direction of the first induced electromotive force is opposite to the direction of the second induced electromotive force, and the induced voltage value of the first induced electromotive force is the same as the induced voltage value of the second induced electromotive force.

[0049] Specifically, when the magnetic field passes through the loop in the vertical direction, an electromotive force will be formed on the mounted resistor. Since the 2N mounted resistors are symmetrically arranged and the number of mounted resistors in each loop is even, the electromotive forces cancel each other out, thereby reducing the electromagnetic interference of the alternating magnetic field on the loop in the direction perpendicular to the circuit board.

[0050] The working principle of the anti-alternating magnetic field interference circuit of the voltage sampling loop proposed by the present invention will be further described below through a specific example.

[0051] As Figure 5 shown, taking N = 3 as an example, six metal foil resistors are selected and two loops with opposite currents and as equal areas as possible are formed by cross-wired traces.

[0052] The area of loop A1 is approximately 120 mm 2 , and the area of loop A2 is approximately 110 mm 2 . Assuming that there is an alternating magnetic field perpendicular to the loop plane around the circuit, and the magnetic field strength B(t) is 0.2 mT, and the magnetic field frequency is 50 Hz, substituting into formulas (1)-(3), the effective value V RMS of the induced voltage generated in loop A1 of the circuit is calculated to be approximately 5.3 μV; the current in loop A2 is in the opposite direction, and the effective value V RMS of the generated induced voltage is approximately -4.9 μV. Therefore, the effective value of the induced voltage generated in this circuit is 0.4 μV, which is about 23 times lower than the induced voltage generated in the Figure 3 circuit layout, greatly reducing the influence of the alternating magnetic field on the loop in the horizontal direction of the circuit.

[0053] In this circuit design, it is necessary to ensure that the number of inserted resistors in each loop is even and they are symmetrically arranged. Assuming that there is a magnetic field passing through the loop formed by the inserted resistors in the direction perpendicular to the circuit board, an electromotive force will be formed at both ends of the resistor. As shown in the figure, in loop A1, the induced electromotive forces formed by metal foil resistor R2 and metal foil resistor R3 are opposite in direction to those formed by metal foil resistor R4 and metal foil resistor R5 and cancel each other out; in loop A2, the induced electromotive forces formed by metal foil resistor R1 and metal foil resistor R6 also cancel each other out. Therefore, the symmetric arrangement of the inserted resistors can effectively reduce the interference of the alternating magnetic field on the circuit in the vertical direction.

[0054] The anti-alternating magnetic field interference circuit of the voltage sampling circuit proposed by the present utility model has the following beneficial effects:

[0055] (1) For the problem of interference of the alternating magnetic field on the horizontal direction of the circuit, a cross-wiring circuit layout method is adopted. By forming an even number of loops in the circuit, and the current directions of the loops are opposite and the areas are as equal as possible, so as to achieve the mutual cancellation of magnetic field interference and enhance the internal neutralization ability of the circuit to external electromagnetic interference;

[0056] (2) For the problem of interference of the alternating magnetic field on the vertical direction of the circuit, a new device layout method is adopted. In each circuit loop, the number of inserted resistors is selected to be even and arranged symmetrically to ensure that the electromotive forces formed on the inserted devices cancel each other out under the interference of the alternating magnetic field, and reduce the electromagnetic interference of the alternating magnetic field on the loop in the direction perpendicular to the circuit board;

[0057] (3) By optimizing the circuit layout and device layout, the effect of electromagnetic shielding is achieved, with low cost and easy implementation.

[0058] Secondly, a standard watt-hour meter provided by the present utility model adopts the above anti-alternating magnetic field interference circuit of the voltage sampling circuit.

[0059] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or N embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0060] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present utility model, the meaning of "N" is at least two, such as two, three, etc., unless otherwise specifically defined.

Claims

1. An anti-alternating magnetic field interference circuit for a voltage sampling circuit, characterized in that, Including: An input terminal and an output terminal, the positive pole of the input terminal is for signal input, the positive pole of the output terminal is for signal output, and the negative poles of both the input terminal and the output terminal are grounded; 2N plug-in resistors, where N is a positive integer greater than or equal to 2. The 2N plug-in resistors are symmetrically placed. The first plug-in resistor is connected to the other side of the input terminal, the 2Nth plug-in resistor is connected to the other side of the output terminal, and the 2N plug-in resistors are connected in series by cross-wiring, forming 2M loops, where M is a positive integer.

2. The anti-alternating magnetic field interference circuit of the voltage sampling circuit according to claim 1, characterized in that The 2N plug-in resistors are connected to a target circuit board, and the target circuit board is perpendicular to the alternating magnetic field.

3. The anti-alternating magnetic field interference circuit of the voltage sampling circuit according to claim 1, wherein The specifications of each plug-in resistor are the same.

4. The anti-alternating magnetic field interference circuit of the voltage sampling circuit according to claim 1, characterized in that, The current directions of each loop are opposite, and the loop areas of each loop tend to be the same.

5. The anti-alternating magnetic field interference circuit of the voltage sampling circuit according to claim 4, characterized in that, In each loop, the symmetric plug-in resistors respectively form a first induced electromotive force and a second induced electromotive force, and the direction of the first induced electromotive force is opposite to the direction of the second induced electromotive force, and the induced voltage value of the first induced electromotive force is the same as the induced voltage value of the second induced electromotive force.

6. A standard electricity meter, characterized in that, The standard watt-hour meter adopts the anti-alternating magnetic field interference circuit of the voltage sampling circuit according to any one of claims 1-5.

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